diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 7acfef6d2..6d5a8aa0f 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,9 +1,47 @@
-name: CI on Windows
+name: CI
 
 on: [push, pull_request]
 
 jobs:
-  build:
+  ubuntu:
+    runs-on: ubuntu-16.04
+    strategy:
+      fail-fast: false
+      matrix:
+        name: [py36, py37, py38]
+        include:
+        - name: py36
+          python: 3.6
+          docutils: du13
+        - name: py37
+          python: 3.7
+          docutils: du14
+        - name: py38
+          python: 3.8
+          docutils: du15
+          coverage: "--cov ./ --cov-append --cov-config setup.cfg"
+    env:
+      PYTEST_ADDOPTS: ${{ matrix.coverage }}
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python }}
+    - name: Check Python version
+      run: python --version
+    - name: Install graphviz
+      run: sudo apt-get install graphviz
+    - name: Install dependencies
+      run: pip install -U tox codecov
+    - name: Run Tox
+      run: tox -e ${{ matrix.docutils }} -- -vv
+    - name: codecov
+      uses: codecov/codecov-action@v1
+      if: matrix.coverage
+
+  windows:
     runs-on: windows-latest
     strategy:
       matrix:
diff --git a/.github/workflows/nodejs.yml b/.github/workflows/nodejs.yml
new file mode 100644
index 000000000..d7a7c95f1
--- /dev/null
+++ b/.github/workflows/nodejs.yml
@@ -0,0 +1,21 @@
+name: CI (node.js)
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    env:
+      node-version: 10.7
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Use Node.js ${{ env.node-version }}
+      uses: actions/setup-node@v1
+      with:
+        node-version: ${{ env.node-version }}
+    - run: npm install
+    - name: Run headless test
+      uses: GabrielBB/xvfb-action@v1
+      with:
+        run: npm test
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index fdeec0112..000000000
--- a/.travis.yml
+++ /dev/null
@@ -1,43 +0,0 @@
-os: linux
-dist: xenial
-language: python
-cache: pip
-
-env:
-  global:
-    - PYTHONFAULTHANDLER=x
-    - SKIP_LATEX_BUILD=1
-    - IS_PYTHON=true
-
-jobs:
-  include:
-    - python: '3.6'
-      env:
-        - TOXENV=du14
-    - python: '3.7'
-      env:
-        - TOXENV=du15
-    - python: '3.8'
-      env:
-        - TOXENV=du16
-        - PYTEST_ADDOPTS="--cov ./ --cov-append --cov-config setup.cfg"
-    - python: '3.9'
-      env:
-        - TOXENV=py39
-
-    - language: node_js
-      node_js: '10.7'
-      env: IS_PYTHON=false
-      services: xvfb
-
-install:
-  - "sudo apt-get install graphviz"
-  - if [ $IS_PYTHON = true ]; then pip install -U tox codecov; fi
-  - if [ $IS_PYTHON = false ]; then npm install; fi
-
-script:
-  - if [ $IS_PYTHON = true ]; then tox -- -vv; fi
-  - if [ $IS_PYTHON = false ]; then npm test; fi
-
-after_success:
-  - if [[ -e .coverage ]]; then codecov -e $TOXENV; fi
diff --git a/CHANGES b/CHANGES
index d1506694d..208bd2715 100644
--- a/CHANGES
+++ b/CHANGES
@@ -64,9 +64,15 @@ Deprecated
 Features added
 --------------
 
+* #6914: Add a new event :event:`warn-missing-reference` to custom warning
+  messages when failed to resolve a cross-reference
+* #6914: Emit a detailed warning when failed to resolve a ``:ref:`` reference
+
 Bugs fixed
 ----------
 
+* #7613: autodoc: autodoc does not respect __signature__ of the class
+
 Testing
 --------
 
diff --git a/doc/develop.rst b/doc/develop.rst
index 1287a6539..3bbc220b8 100644
--- a/doc/develop.rst
+++ b/doc/develop.rst
@@ -22,9 +22,9 @@ Extensions
 
 To learn how to write your own extension, see :ref:`dev-extensions`.
 
-The `sphinx-contrib <https://bitbucket.org/birkenfeld/sphinx-contrib/>`_
-repository contains many contributed extensions.  Some of them have their own
-releases on PyPI, others you can install from a checkout.
+The `sphinx-contrib <https://github.com/sphinx-contrib>`_ repository contains many
+contributed extensions.  Some of them have their own releases on PyPI, others you
+can install from a checkout.
 
 This is the current list of contributed extensions in that repository:
 
diff --git a/doc/extdev/appapi.rst b/doc/extdev/appapi.rst
index df3eb3d67..9f2c10676 100644
--- a/doc/extdev/appapi.rst
+++ b/doc/extdev/appapi.rst
@@ -186,6 +186,7 @@ type for that event::
       13. apply post-transforms (by priority): docutils.document -> docutils.document
       14. event.doctree-resolved(app, doctree, docname)
           - (for any reference node that fails to resolve) event.missing-reference(env, node, contnode)
+          - (for any reference node that fails to resolve) event.warn-missing-reference(domain, node)
 
    15. Generate output files
    16. event.build-finished(app, exception)
@@ -284,6 +285,14 @@ Here is a more detailed list of these events.
 
    .. versionadded:: 0.5
 
+.. event:: warn-missing-reference (app, domain, node)
+
+   Emitted when a cross-reference to an object cannot be resolved even after
+   :event:`missing-reference`.  If the event handler can emit warnings for
+   the missing reference, it should return ``True``.
+
+   .. versionadded:: 3.4
+
 .. event:: doctree-resolved (app, doctree, docname)
 
    Emitted when a doctree has been "resolved" by the environment, that is, all
diff --git a/sphinx/domains/std.py b/sphinx/domains/std.py
index 198548410..aa4793b66 100644
--- a/sphinx/domains/std.py
+++ b/sphinx/domains/std.py
@@ -595,8 +595,6 @@ class StandardDomain(Domain):
 
     dangling_warnings = {
         'term': 'term not in glossary: %(target)s',
-        'ref':  'undefined label: %(target)s (if the link has no caption '
-                'the label must precede a section header)',
         'numref':  'undefined label: %(target)s',
         'keyword': 'unknown keyword: %(target)s',
         'doc': 'unknown document: %(target)s',
@@ -1075,8 +1073,23 @@ class StandardDomain(Domain):
             return None
 
 
+def warn_missing_reference(app: "Sphinx", domain: Domain, node: pending_xref) -> bool:
+    if domain.name != 'std' or node['reftype'] != 'ref':
+        return None
+    else:
+        target = node['reftarget']
+        if target not in domain.anonlabels:  # type: ignore
+            msg = __('undefined label: %s')
+        else:
+            msg = __('Failed to create a cross reference. A title or caption not found: %s')
+
+        logger.warning(msg % target, location=node, type='ref', subtype=node['reftype'])
+        return True
+
+
 def setup(app: "Sphinx") -> Dict[str, Any]:
     app.add_domain(StandardDomain)
+    app.connect('warn-missing-reference', warn_missing_reference)
 
     return {
         'version': 'builtin',
diff --git a/sphinx/events.py b/sphinx/events.py
index ff753b3b6..59d38daf0 100644
--- a/sphinx/events.py
+++ b/sphinx/events.py
@@ -45,6 +45,7 @@ core_events = {
     'doctree-read': 'the doctree before being pickled',
     'env-merge-info': 'env, read docnames, other env instance',
     'missing-reference': 'env, node, contnode',
+    'warn-missing-reference': 'domain, node',
     'doctree-resolved': 'doctree, docname',
     'env-updated': 'env',
     'html-collect-pages': 'builder',
diff --git a/sphinx/ext/autodoc/__init__.py b/sphinx/ext/autodoc/__init__.py
index 4c28d7b3c..482b48d88 100644
--- a/sphinx/ext/autodoc/__init__.py
+++ b/sphinx/ext/autodoc/__init__.py
@@ -1376,7 +1376,12 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
         # This sequence is copied from inspect._signature_from_callable.
         # ValueError means that no signature could be found, so we keep going.
 
-        # First, let's see if it has an overloaded __call__ defined
+        # First, we check the obj has a __signature__ attribute
+        if (hasattr(self.object, '__signature__') and
+                isinstance(self.object.__signature__, Signature)):
+            return None, None, self.object.__signature__
+
+        # Next, let's see if it has an overloaded __call__ defined
         # in its metaclass
         call = get_user_defined_function_or_method(type(self.object), '__call__')
 
diff --git a/sphinx/transforms/post_transforms/__init__.py b/sphinx/transforms/post_transforms/__init__.py
index 7dc14af52..6633d6434 100644
--- a/sphinx/transforms/post_transforms/__init__.py
+++ b/sphinx/transforms/post_transforms/__init__.py
@@ -166,7 +166,10 @@ class ReferencesResolver(SphinxPostTransform):
                     warn = False
         if not warn:
             return
-        if domain and typ in domain.dangling_warnings:
+
+        if self.app.emit_firstresult('warn-missing-reference', domain, node):
+            return
+        elif domain and typ in domain.dangling_warnings:
             msg = domain.dangling_warnings[typ]
         elif node.get('refdomain', 'std') not in ('', 'std'):
             msg = (__('%s:%s reference target not found: %%(target)s') %
diff --git a/tests/roots/test-domain-py-xref-warning/conf.py b/tests/roots/test-domain-py-xref-warning/conf.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/roots/test-domain-py-xref-warning/index.rst b/tests/roots/test-domain-py-xref-warning/index.rst
new file mode 100644
index 000000000..6f2cab795
--- /dev/null
+++ b/tests/roots/test-domain-py-xref-warning/index.rst
@@ -0,0 +1,7 @@
+test-domain-py-xref-warning
+===========================
+
+.. _existing-label:
+
+:ref:`no-label`
+:ref:`existing-label`
diff --git a/tests/roots/test-ext-autodoc/target/classes.py b/tests/roots/test-ext-autodoc/target/classes.py
index dc471a6f3..52c23748b 100644
--- a/tests/roots/test-ext-autodoc/target/classes.py
+++ b/tests/roots/test-ext-autodoc/target/classes.py
@@ -1,3 +1,6 @@
+from inspect import Parameter, Signature
+
+
 class Foo:
     pass
 
@@ -10,3 +13,11 @@ class Bar:
 class Baz:
     def __new__(cls, x, y):
         pass
+
+
+class Qux:
+    __signature__ = Signature(parameters=[Parameter('foo', Parameter.POSITIONAL_OR_KEYWORD),
+                                          Parameter('bar', Parameter.POSITIONAL_OR_KEYWORD)])
+
+    def __init__(self, x, y):
+        pass
diff --git a/tests/test_domain_py.py b/tests/test_domain_py.py
index eb3afae1d..e9facc0e2 100644
--- a/tests/test_domain_py.py
+++ b/tests/test_domain_py.py
@@ -876,3 +876,11 @@ def test_noindexentry(app):
     assert_node(doctree, (addnodes.index, desc, addnodes.index, desc))
     assert_node(doctree[0], addnodes.index, entries=[('single', 'f (built-in class)', 'f', '', None)])
     assert_node(doctree[2], addnodes.index, entries=[])
+
+
+@pytest.mark.sphinx('dummy', testroot='domain-py-xref-warning')
+def test_warn_missing_reference(app, status, warning):
+    app.build()
+    assert 'index.rst:6: WARNING: undefined label: no-label' in warning.getvalue()
+    assert ('index.rst:6: WARNING: Failed to create a cross reference. A title or caption not found: existing-label'
+            in warning.getvalue())
diff --git a/tests/test_ext_autodoc.py b/tests/test_ext_autodoc.py
index c0676f23f..703cc13f6 100644
--- a/tests/test_ext_autodoc.py
+++ b/tests/test_ext_autodoc.py
@@ -1832,19 +1832,26 @@ def test_autodoc_for_egged_code(app):
 def test_singledispatch(app):
     options = {"members": None}
     actual = do_autodoc(app, 'module', 'target.singledispatch', options)
-    assert list(actual) == [
-        '',
-        '.. py:module:: target.singledispatch',
-        '',
-        '',
-        '.. py:function:: func(arg, kwarg=None)',
-        '                 func(arg: int, kwarg=None)',
-        '                 func(arg: str, kwarg=None)',
-        '   :module: target.singledispatch',
-        '',
-        '   A function for general use.',
-        '',
-    ]
+    if sys.version_info < (3, 6):
+        # check the result via "in" because the order of singledispatch signatures is
+        # usually changed (because dict is not OrderedDict yet!)
+        assert '.. py:function:: func(arg, kwarg=None)' in actual
+        assert '                 func(arg: int, kwarg=None)' in actual
+        assert '                 func(arg: str, kwarg=None)' in actual
+    else:
+        assert list(actual) == [
+            '',
+            '.. py:module:: target.singledispatch',
+            '',
+            '',
+            '.. py:function:: func(arg, kwarg=None)',
+            '                 func(arg: int, kwarg=None)',
+            '                 func(arg: str, kwarg=None)',
+            '   :module: target.singledispatch',
+            '',
+            '   A function for general use.',
+            '',
+        ]
 
 
 @pytest.mark.skipif(sys.version_info < (3, 8),
diff --git a/tests/test_ext_autodoc_autoclass.py b/tests/test_ext_autodoc_autoclass.py
new file mode 100644
index 000000000..89a79c2c7
--- /dev/null
+++ b/tests/test_ext_autodoc_autoclass.py
@@ -0,0 +1,50 @@
+"""
+    test_ext_autodoc_autoclass
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    Test the autodoc extension.  This tests mainly the Documenters; the auto
+    directives are tested in a test source file translated by test_build.
+
+    :copyright: Copyright 2007-2020 by the Sphinx team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+import pytest
+
+from test_ext_autodoc import do_autodoc
+
+
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_classes(app):
+    actual = do_autodoc(app, 'function', 'target.classes.Foo')
+    assert list(actual) == [
+        '',
+        '.. py:function:: Foo()',
+        '   :module: target.classes',
+        '',
+    ]
+
+    actual = do_autodoc(app, 'function', 'target.classes.Bar')
+    assert list(actual) == [
+        '',
+        '.. py:function:: Bar(x, y)',
+        '   :module: target.classes',
+        '',
+    ]
+
+    actual = do_autodoc(app, 'function', 'target.classes.Baz')
+    assert list(actual) == [
+        '',
+        '.. py:function:: Baz(x, y)',
+        '   :module: target.classes',
+        '',
+    ]
+
+    actual = do_autodoc(app, 'function', 'target.classes.Qux')
+    assert list(actual) == [
+        '',
+        '.. py:function:: Qux(foo, bar)',
+        '   :module: target.classes',
+        '',
+    ]
+
diff --git a/tests/test_ext_autodoc_autofunction.py b/tests/test_ext_autodoc_autofunction.py
index bb292bc6a..3c8165995 100644
--- a/tests/test_ext_autodoc_autofunction.py
+++ b/tests/test_ext_autodoc_autofunction.py
@@ -9,6 +9,8 @@
     :license: BSD, see LICENSE for details.
 """
 
+import sys
+
 import pytest
 
 from test_ext_autodoc import do_autodoc
@@ -40,6 +42,14 @@ def test_classes(app):
         '',
     ]
 
+    actual = do_autodoc(app, 'function', 'target.classes.Qux')
+    assert list(actual) == [
+        '',
+        '.. py:function:: Qux(foo, bar)',
+        '   :module: target.classes',
+        '',
+    ]
+
 
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
 def test_callable(app):
@@ -108,16 +118,23 @@ def test_decorated(app):
 def test_singledispatch(app):
     options = {}
     actual = do_autodoc(app, 'function', 'target.singledispatch.func', options)
-    assert list(actual) == [
-        '',
-        '.. py:function:: func(arg, kwarg=None)',
-        '                 func(arg: int, kwarg=None)',
-        '                 func(arg: str, kwarg=None)',
-        '   :module: target.singledispatch',
-        '',
-        '   A function for general use.',
-        '',
-    ]
+    if sys.version_info < (3, 6):
+        # check the result via "in" because the order of singledispatch signatures is
+        # usually changed (because dict is not OrderedDict yet!)
+        assert '.. py:function:: func(arg, kwarg=None)' in actual
+        assert '                 func(arg: int, kwarg=None)' in actual
+        assert '                 func(arg: str, kwarg=None)' in actual
+    else:
+        assert list(actual) == [
+            '',
+            '.. py:function:: func(arg, kwarg=None)',
+            '                 func(arg: int, kwarg=None)',
+            '                 func(arg: str, kwarg=None)',
+            '   :module: target.singledispatch',
+            '',
+            '   A function for general use.',
+            '',
+        ]
 
 
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
diff --git a/tox.ini b/tox.ini
index 01881dd97..3d40d2f97 100644
--- a/tox.ini
+++ b/tox.ini
@@ -24,7 +24,7 @@ extras =
     test
 setenv =
     PYTHONWARNINGS = all,ignore::ImportWarning:importlib._bootstrap_external,ignore::DeprecationWarning:site,ignore::DeprecationWarning:distutils
-    PYTEST_ADDOPTS = --color yes
+    PYTEST_ADDOPTS = {env:PYTEST_ADDOPTS:} --color yes
 commands=
     pytest --durations 25 {posargs}