remove usage of pylib in docs

Author: asottile

doc/en/example/assertion/global_testmodule_config/conftest.py

@@ -1,8 +1,8 @@
-import py
+import os.path
 
 import pytest
 
-mydir = py.path.local(__file__).dirpath()
+mydir = os.path.dirname(__file__)
 
 
 def pytest_runtest_setup(item):

doc/en/example/assertion/test_failures.py

@@ -1,13 +1,13 @@
-import py
+import os.path
+import shutil
 
-failure_demo = py.path.local(__file__).dirpath("failure_demo.py")
+failure_demo = os.path.join(os.path.dirname(__file__), "failure_demo.py")
 pytest_plugins = ("pytester",)
 
 
 def test_failure_demo_fails_properly(testdir):
-    target = testdir.tmpdir.join(failure_demo.basename)
-    failure_demo.copy(target)
-    failure_demo.copy(testdir.tmpdir.join(failure_demo.basename))
+    target = testdir.tmpdir.join(os.path.basename(failure_demo))
+    shutil.copy(failure_demo, target)
     result = testdir.runpytest(target, syspathinsert=True)
     result.stdout.fnmatch_lines(["*44 failed*"])
     assert result.ret != 0