Drop Python 2.7 and 3.4 support

* Update setup.py requires and classifiers
* Drop Python 2.7 and 3.4 from CI
* Update docs dropping 2.7 and 3.4 support
* Fix mock imports and remove tests related to pypi's mock module
* Add py27 and 34 support docs to the sidebar
* Remove usage of six from tmpdir
* Remove six.PY* code blocks
* Remove sys.version_info related code
* Cleanup compat
* Remove obsolete safe_str
* Remove obsolete __unicode__ methods
* Remove compat.PY35 and compat.PY36: not really needed anymore
* Remove unused UNICODE_TYPES
* Remove Jython specific code
* Remove some Python 2 references from docs

Related to #5275

testing/python/approx.py

@@ -1,7 +1,6 @@
 # -*- coding: utf-8 -*-
 import doctest
 import operator
-import sys
 from decimal import Decimal
 from fractions import Fraction
 from operator import eq
@@ -28,7 +27,7 @@ class MyDocTestRunner(doctest.DocTestRunner):
 class TestApprox(object):
     @pytest.fixture
     def plus_minus(self):
-        return u"\u00b1" if sys.version_info[0] > 2 else u"+-"
+        return u"\u00b1"
 
     def test_repr_string(self, plus_minus):
         tol1, tol2, infr = "1.0e-06", "2.0e-06", "inf"

testing/python/collect.py

@@ -679,8 +679,6 @@ class TestSorting(object):
 
         assert fn1 == fn2
         assert fn1 != modcol
-        if sys.version_info < (3, 0):
-            assert cmp(fn1, fn2) == 0  # NOQA
         assert hash(fn1) == hash(fn2)
 
         fn3 = testdir.collect_by_name(modcol, "test_fail")

testing/python/metafunc.py

@@ -13,8 +13,6 @@ from _pytest import fixtures
 from _pytest import python
 from _pytest.warnings import SHOW_PYTEST_WARNINGS_ARG
 
-PY3 = sys.version_info >= (3, 0)
-
 
 class TestMetafunc(object):
     def Metafunc(self, func, config=None):

testing/python/raises.py

@@ -1,8 +1,6 @@
 # -*- coding: utf-8 -*-
 import sys
 
-import six
-
 import pytest
 from _pytest.outcomes import Failed
 from _pytest.warning_types import PytestDeprecationWarning
@@ -265,16 +263,7 @@ class TestRaises(object):
             def __class__(self):
                 assert False, "via __class__"
 
-        if six.PY2:
-            with pytest.raises(pytest.fail.Exception) as excinfo:
-                with pytest.raises(CrappyClass()):
-                    pass
-            assert "DID NOT RAISE" in excinfo.value.args[0]
-
-            with pytest.raises(CrappyClass) as excinfo:
-                raise CrappyClass()
-        else:
-            with pytest.raises(AssertionError) as excinfo:
-                with pytest.raises(CrappyClass()):
-                    pass
-            assert "via __class__" in excinfo.value.args[0]
+        with pytest.raises(AssertionError) as excinfo:
+            with pytest.raises(CrappyClass()):
+                pass
+        assert "via __class__" in excinfo.value.args[0]