Fix PyPy datetime mock issue and extension test issue

PR #3083

* Don't test C reify when testing with no extensions

* Skip test_access_logger_atoms under PyPy

It fails because PyPy, unlike CPython, has pure-python implementation
of datetime and when it's patched, it fails on isinstance check in
magic methods.

Ref: https://bitbucket.org/pypy/pypy/issues/1187/call-to-isinstance-in-__sub__-self-other
Ref: celery/celery#811
Ref: https://stackoverflow.com/a/46102240/595220

* Disallow PyPy3 failures

* Don't test C-reify under PyPy

* Don't run test_warning_checks under PyPy

* Expect different outcome for PyPy + ASYNCIODEBUG

.travis.yml

@@ -135,7 +135,6 @@ jobs:
   fast_finish: true
   allow_failures:
   - python: nightly
-  - python: *pypy3
 
   include:
   - <<: *_doc_base

tests/test_helpers.py

@@ -2,6 +2,7 @@
 import datetime
 import gc
 import os
+import platform
 import tempfile
 from unittest import mock
 
@@ -12,6 +13,9 @@
 from aiohttp.abc import AbstractAccessLogger
 
 
+IS_PYPY = platform.python_implementation() == 'PyPy'
+
+
 # ------------------- parse_mimetype ----------------------------------
 
 @pytest.mark.parametrize('mimetype, expected', [
@@ -124,6 +128,29 @@ def test_access_logger_format():
     assert expected == access_logger._log_format
 
 
+@pytest.mark.skip(
+    IS_PYPY,
+    """
+    Because of patching :py:class:`datetime.datetime`, under PyPy it
+    fails in :py:func:`isinstance` call in
+    :py:meth:`datetime.datetime.__sub__` (called from
+    :py:meth:`aiohttp.helpers.AccessLogger._format_t`):
+
+    *** TypeError: isinstance() arg 2 must be a class, type, or tuple of classes and types
+
+    (Pdb) from datetime import datetime
+    (Pdb) isinstance(now, datetime)
+    *** TypeError: isinstance() arg 2 must be a class, type, or tuple of classes and types
+    (Pdb) datetime.__class__
+    <class 'unittest.mock.MagicMock'>
+    (Pdb) isinstance(now, datetime.__class__)
+    False
+
+    Ref: https://bitbucket.org/pypy/pypy/issues/1187/call-to-isinstance-in-__sub__-self-other
+    Ref: https://github.com/celery/celery/issues/811
+    Ref: https://stackoverflow.com/a/46102240/595220
+    """,  # noqa: E501
+)
 def test_access_logger_atoms(mocker):
     utcnow = datetime.datetime(1843, 1, 1, 0, 30)
     mock_datetime = mocker.patch("aiohttp.helpers.datetime.datetime")
@@ -289,8 +316,9 @@ class TestPyReify(ReifyMixin):
     reify = helpers.reify_py
 
 
-class TestCReify(ReifyMixin):
-    reify = helpers.reify_c
+if not helpers.NO_EXTENSIONS and not IS_PYPY:
+    class TestCReify(ReifyMixin):
+        reify = helpers.reify_c
 
 # ----------------------------------- is_ip_address() ----------------------
 

tests/test_pytest_plugin.py

@@ -1,3 +1,5 @@
+import os
+import platform
 import sys
 
 import pytest
@@ -10,6 +12,9 @@
 '''
 
 
+IS_PYPY = platform.python_implementation() == 'PyPy'
+
+
 def test_aiohttp_plugin(testdir):
     testdir.makepyfile("""\
 import pytest
@@ -163,7 +168,13 @@ async def test_bad():
     testdir.makeconftest(CONFTEST)
     result = testdir.runpytest('-p', 'no:sugar', '-s', '-W',
                                'default', '--aiohttp-loop=pyloop')
-    result.assert_outcomes(passed=1, failed=1)
+    expected_outcomes = (
+        {'failed': 0, 'passed': 2}
+        if IS_PYPY and bool(os.environ.get('PYTHONASYNCIODEBUG'))
+        else {'failed': 1, 'passed': 1}
+    )
+    """Under PyPy "coroutine 'foobar' was never awaited" does not happen."""
+    result.assert_outcomes(**expected_outcomes)
 
 
 def test_aiohttp_plugin_async_fixture(testdir, capsys):