Make pytest the test runner.

setup.py

@@ -117,7 +117,7 @@ setup(
     setup_requires=[
         'setuptools_scm',
     ],
-    tests_require=['tox', 'nose', 'scripttest', 'mock', 'hypothesis'],
+    tests_require=['tox', 'pytest', 'pytest-cov', 'nose', 'scripttest', 'mock', 'hypothesis'],
     cmdclass={'test': Tox},
     entry_points={
         'console_scripts': [

tox.ini

@@ -6,8 +6,10 @@ deps = nose
        coverage
        scripttest
        mock
+       pytest
+       pytest-cov
        hypothesis
-commands = nosetests --with-coverage --cover-erase --cover-branches
+commands = py.test
 
 [testenv:docs]
 basepython = python