tests: fix_test_build_deps_on_distutils

* ignore distutils' warning (`Unknown distribution option: 'python_requires'`)
* fix test on Windows

setuptools/tests/test_integration.py

@@ -141,6 +141,7 @@ def test_build_deps_on_distutils(request, tmpdir_factory, build_dep):
         allowed_unknowns = [
             'test_suite',
             'tests_require',
+            'python_requires',
             'install_requires',
         ]
         assert not match or match.group(1).strip('"\'') in allowed_unknowns
@@ -149,8 +150,8 @@ def test_build_deps_on_distutils(request, tmpdir_factory, build_dep):
 def install(pkg_dir, install_dir):
     with open(os.path.join(pkg_dir, 'setuptools.py'), 'w') as breaker:
         breaker.write('raise ImportError()')
-    cmd = [sys.executable, 'setup.py', 'install', '--prefix', install_dir]
-    env = dict(os.environ, PYTHONPATH=pkg_dir)
+    cmd = [sys.executable, 'setup.py', 'install', '--prefix', str(install_dir)]
+    env = dict(os.environ, PYTHONPATH=str(pkg_dir))
     output = subprocess.check_output(
         cmd, cwd=pkg_dir, env=env, stderr=subprocess.STDOUT)
     return output.decode('utf-8')