makeapi, makeaci: do not fail on missing imports

Add import hook to makeapi and makeaci which makes them ignore import
errors in modules in our source tree and instead print a warning.

This makes it possible to build IPA without having to have most of our
runtime dependencies installed.

https://fedorahosted.org/freeipa/ticket/6418

Reviewed-By: Petr Spacek <pspacek@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>

freeipa.spec.in

@@ -89,22 +89,11 @@ BuildRequires:  python-lesscpy
 #
 BuildRequires:  krb5-workstation
 BuildRequires:  python-ldap
-BuildRequires:  python-setuptools
 BuildRequires:  python-nss
-# 0.6: serialization.load_pem_private_key, load_pem_public_key
-BuildRequires:  python-cryptography >= 0.6
 BuildRequires:  python-netaddr
-BuildRequires:  python-gssapi
-BuildRequires:  python-libipa_hbac
-BuildRequires:  python-memcached
-BuildRequires:  python-lxml
 BuildRequires:  python-pyasn1
 BuildRequires:  python-dns
-# pki Python package
-BuildRequires:  pki-base
 BuildRequires:  python-six
-BuildRequires:  dbus-python
-BuildRequires:  python-netifaces
 BuildRequires:  python-libsss_nss_idmap
 BuildRequires:  python-cffi
 
@@ -113,22 +102,32 @@ BuildRequires:  python-cffi
 #
 %if 0%{?with_lint}
 BuildRequires:  samba-python
+BuildRequires:  python-setuptools
+# 0.6: serialization.load_pem_private_key, load_pem_public_key
+BuildRequires:  python-cryptography >= 0.6
+BuildRequires:  python-gssapi
 BuildRequires:  pylint >= 1.0
 # workaround for https://bugzilla.redhat.com/show_bug.cgi?id=1096506
 BuildRequires:  python2-polib
+BuildRequires:  python-libipa_hbac
+BuildRequires:  python-memcached
+BuildRequires:  python-lxml
 # 5.0.0: QRCode.print_ascii
 BuildRequires:  python-qrcode-core >= 5.0.0
 # 1.11.0: resolver.YXDOMAIN, Resolver.set_flags
 BuildRequires:  python-dns >= 1.11.0
 BuildRequires:  jsl
 BuildRequires:  python-yubico
+# pki Python package
 # 10.2.1: crypto.NSSCryptoProvider(password_file)
 BuildRequires:  pki-base >= 10.2.1
 BuildRequires:  python-pytest-multihost
 BuildRequires:  python-pytest-sourceorder
 BuildRequires:  python-jwcrypto
 BuildRequires:  python-custodia
+BuildRequires:  dbus-python
 BuildRequires:  python-dateutil
+BuildRequires:  python-netifaces
 BuildRequires:  python-sss
 BuildRequires:  python-sss-murmur
 BuildRequires:  python-sssdconfig

ignore_import_errors.py

@@ -0,0 +1,87 @@
+#
+# Copyright (C) 2016  FreeIPA Contributors see COPYING for license
+#
+
+"""
+ImportError ignoring import hook.
+"""
+
+from __future__ import print_function
+
+import imp
+import inspect
+import os.path
+import sys
+
+DIRNAME = os.path.dirname(os.path.abspath(__file__))
+
+
+class FailedImport(object):
+    def __init__(self, loader, name):
+        self.__file__ = __file__
+        self.__name__ = name
+        self.__path__ = []
+        self.__loader__ = loader
+        self.__package__ = name
+
+    def __repr__(self):
+        return '<failed import {!r}>'.format(self.__name__)
+
+
+class IgnoringImporter(object):
+    def find_module(self, fullname, path=None):
+        parentname, dot, name = fullname.rpartition('.')
+        assert (not dot and path is None) or (dot and path is not None)
+
+        # check if the module can be found
+        try:
+            file, _filename, _description = imp.find_module(name, path)
+        except ImportError:
+            pass
+        else:
+            if file is not None:
+                file.close()
+            # it can be found, do normal import
+            return None
+
+        # check if the parent module import failed
+        if dot and isinstance(sys.modules[parentname], FailedImport):
+            # it did fail, so this import will fail as well
+            return self
+
+        # find out from where are we importing
+        if path is None:
+            path = sys.path
+        for pathname in path:
+            pathname = os.path.abspath(pathname)
+            if not pathname.startswith(DIRNAME):
+                break
+        else:
+            # importing from our source tree, do normal import
+            return None
+
+        # find out into what .py file are we importing
+        frame = inspect.currentframe().f_back
+        filename = frame.f_code.co_filename
+        if filename.startswith('<'):
+            # not a file, do normal import
+            return None
+        filename = os.path.abspath(filename)
+        if not filename.startswith(DIRNAME):
+            # not a file in our source tree, do normal import
+            return None
+
+        return self
+
+    def load_module(self, fullname):
+        frame = inspect.currentframe().f_back
+        print("{}: {}:{}: ignoring ImportError: No module named {}".format(
+                sys.argv[0],
+                os.path.relpath(frame.f_code.co_filename),
+                frame.f_lineno,
+                fullname))
+
+        return sys.modules.setdefault(fullname, FailedImport(self, fullname))
+
+
+sys.meta_path.insert(0, IgnoringImporter())

makeaci

@@ -30,6 +30,8 @@ import sys
 import difflib
 from argparse import ArgumentParser
 
+import ignore_import_errors     # pylint: disable=unused-import
+
 from ipalib import api
 from ipapython.dn import DN
 from ipapython.ipaldap import LDAPClient

makeapi

@@ -32,6 +32,9 @@ import os
 import re
 import inspect
 import operator
+
+import ignore_import_errors     # pylint: disable=unused-import
+
 from ipalib import api
 from ipalib.parameters import Param
 from ipalib.output import Output