Porting tests to pytest (#33387)

* Porting tests to pytest

* Achievement Get: No longer need mock/generator.py
  * Now done via pytest's parametrization
  * Port safe_eval to pytest
  * Port text tests to pytest
  * Port test_set_mode_if_different to pytest

* Change conftest AnsibleModule fixtures to be more flexible
  * Move the AnsibleModules fixtures to module_utils/conftest.py for sharing
  * Testing the argspec code requires:
    * injecting both the argspec and the arguments.
    * Patching the arguments into sys.stdin at a different level

* More porting to obsolete mock/procenv.py
  * Port run_command to pytest
  * Port known_hosts tests to pytest
  * Port safe_eval to pytest
  * Port test_distribution_version.py to pytest
  * Port test_log to pytest
  * Port test__log_invocation to pytest
  * Remove unneeded import of procenv in test_postgresql

* Port test_pip to pytest style
  * As part of this, create a pytest ansiblemodule fixture in
    modules/conftest.py.  This is slightly different than the
    approach taken in module_utils because here we need to override the
    AnsibleModule that the modules will inherit from instead of one that
    we're instantiating ourselves.

* Fixup usage of parametrization in test_deprecate_warn

* Check that the pip module failed in our test

test/units/module_utils/test_postgresql.py

@@ -1,13 +1,13 @@
-import json
+# Copyright (c) 2017 Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
 import sys
 
 from ansible.compat.tests import unittest
 from ansible.compat.tests.mock import patch, MagicMock
 
-from ansible.module_utils.basic import AnsibleModule
 from ansible.module_utils.six.moves import builtins
 from ansible.module_utils._text import to_native
-from units.mock.procenv import swap_stdin_and_argv
 
 
 import pprint