path.common: handle FileNotFoundError when trying to import pathlib

Python 3.4 might raise FileNotFoundError due to `os.getcwd()` failing on
a non-existing cwd.  This is fixed in Python 3.5.

Ref: pytest-dev/pytest#4787 (comment)

py/_path/common.py

@@ -37,6 +37,8 @@ def fspath(path):
                 import pathlib
             except ImportError:
                 pass
+            except FileNotFoundError:  # Might happen in py34.
+                pass
             else:
                 if isinstance(path, pathlib.PurePath):
                     return py.builtin.text(path)

testing/path/test_local.py

@@ -161,7 +161,31 @@ def test_eq_with_strings(self, path1):
         assert path2 != path3
 
     def test_eq_with_none(self, path1):
-        assert path1 != None  # noqa
+        assert path1 != None  # noqa: E711
+
+    @pytest.mark.skipif(
+        sys.platform.startswith("win32"), reason="cannot remove cwd on Windows"
+    )
+    @pytest.mark.skipif(
+        sys.version_info < (3, 0) or sys.version_info >= (3, 5),
+        reason="only with Python 3 before 3.5"
+    )
+    def test_eq_with_none_and_custom_fspath(self, monkeypatch, path1):
+        import os
+        import shutil
+        import tempfile
+
+        d = tempfile.mkdtemp()
+        os.chdir(d)
+        shutil.rmtree(d)
+
+        monkeypatch.delitem(sys.modules, 'pathlib')
+        monkeypatch.setattr(sys, 'path', [''] + sys.path)
+
+        with pytest.raises(FileNotFoundError):
+            import pathlib  # noqa: F401
+
+        assert path1 != None  # noqa: E711
 
     def test_eq_non_ascii_unicode(self, path1):
         path2 = path1.join(u'temp')