fix tests for paths (UNIX/Windows)

- use pathlib for OS-agnostic path comparisons
- install pathlib2 in setup.py for Python 2.7

Author: orbeckst

MDAnalysisData/tests/test_base.py

@@ -4,6 +4,12 @@
 
 from six.moves.urllib.request import urlretrieve
 
+try:
+    import pathlib
+except ImportError:
+    # Python 2.7
+    import pathlib2 as pathlib
+
 import os
 import os.path
 
@@ -60,11 +66,11 @@ def test_sha256(tmpdir, some_text):
     assert checksum == "4446bfb2ec5dedfbd981d059d6005f5144b067b392a00e3bcf98f8302ec8f765"
 
 @pytest.mark.parametrize('data_home,location', [
-    (None, os.path.expanduser("~/MDAnalysis_data")),
-    ("/tmp/MDAnalysisData", "/tmp/MDAnalysisData"),
+    (None, pathlib.Path("~/MDAnalysis_data").expanduser()),
+    (str(pathlib.Path("/tmp/MDAnalysisData")), pathlib.Path("/tmp/MDAnalysisData")),
     ])
 def test_get_data_home(data_home, location):
-    assert base.get_data_home(data_home=data_home) == location
+    assert base.get_data_home(data_home=data_home) == str(location)
 
 def test_clear_data_home(tmpdir, some_text):
     data_home_path = tmpdir.join("MDAnalysis_data_test")

setup.py

@@ -20,6 +20,7 @@
 import versioneer
 
 import os
+import sys
 import warnings
 import codecs
 
@@ -129,6 +130,11 @@ def dynamic_author_list():
         'Topic :: Software Development :: Libraries :: Python Modules',
     ]
 
+    # Python 2.7 compatibility
+    test_requirements = ['pytest', 'pytest-mock']
+    if sys.version_info.major < 3:
+        test_requirements.append("pathlib2")
+
     setup(name='MDAnalysisData',
           version=versioneer.get_version(),
           cmdclass=versioneer.get_cmdclass(),
@@ -155,6 +161,6 @@ def dynamic_author_list():
                             'setuptools',
                             'tqdm',
           ],
-          tests_require=['pytest', 'pytest-mock'],
+          tests_require=test_requirements,
           zip_safe=True,
     )