Replace nose with unittest and pytest

* Replace raise nose.SkipTest with raise unittest.SkipTest
* Replace nose.tools.assert_equal(a, b) with assert a == b
* Replace nose.tools.raises with pytest.raises
* Convert @raises decorator to pytest.raises() but just for relevant
  lines.
* Remove nose dependency

I left the nose_compat pytest plugin in place. It can be removed in
another request in case it is no longer used.

https://pagure.io/freeipa/issue/7301

Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipatests/test_xmlrpc/test_passwd_plugin.py

@@ -19,13 +19,11 @@
 """
 Test the `ipaserver/plugins/passwd.py` module.
 """
-
-from nose.tools import assert_raises  # pylint: disable=E0611
+import pytest
 
 from ipatests.test_xmlrpc.xmlrpc_test import XMLRPC_test, assert_attr_equal
 from ipalib import api
 from ipalib import errors
-import pytest
 
 
 @pytest.mark.tier1
@@ -65,5 +63,5 @@ class test_passwd(XMLRPC_test):
         api.Command['user_del'](self.uid)
 
         # Verify that it is gone
-        with assert_raises(errors.NotFound):
+        with pytest.raises(errors.NotFound):
             api.Command['user_show'](self.uid)