second take at setuptools_scm

since setuptools 18.6 fixes the issues with develop installs

https://github.com/pypa/setuptools/blob/master/CHANGES.rst#186

https://github.com/pypa/setuptools/issues/439

setup.py

@@ -18,15 +18,6 @@ classifiers = ['Development Status :: 6 - Mature',
 with open('README.rst') as fd:
     long_description = fd.read()
 
-def get_version():
-    p = os.path.join(os.path.dirname(
-                     os.path.abspath(__file__)), "_pytest", "__init__.py")
-    with open(p) as f:
-        for line in f.readlines():
-            if "__version__" in line:
-                return line.strip().split("=")[-1].strip(" '")
-    raise ValueError("could not read version")
-
 
 def has_environment_marker_support():
     """
@@ -63,7 +54,9 @@ def main():
         name='pytest',
         description='pytest: simple powerful testing with Python',
         long_description=long_description,
-        version=get_version(),
+        use_scm_version={
+            'write_to': '_pytest/_version.py',
+        },
         url='http://pytest.org',
         license='MIT license',
         platforms=['unix', 'linux', 'osx', 'cygwin', 'win32'],
@@ -74,6 +67,7 @@ def main():
         keywords="test unittest",
         cmdclass={'test': PyTest},
         # the following should be enabled for release
+        setup_requires=['setuptools-scm'],
         install_requires=install_requires,
         extras_require=extras_require,
         packages=['_pytest', '_pytest.assertion', '_pytest._code', '_pytest.vendored_packages'],