Add Runner interface.

testing/resources/python_hooks_repo/foo/main.py

@@ -0,0 +1,6 @@
+import sys
+
+def func():
+    print repr(sys.argv[1:])
+    print 'Hello World'
+    return 0

testing/resources/python_hooks_repo/manifest.yaml

@@ -0,0 +1,4 @@
+-   id: foo
+    name: Foo
+    entry: foo
+    language: python

testing/resources/python_hooks_repo/setup.py

@@ -0,0 +1,11 @@
+from setuptools import find_packages
+from setuptools import setup
+
+setup(
+    name='Foo',
+    version='0.0.0',
+    packages=find_packages('.'),
+    entry_points={
+        'console_scripts': ['foo = foo.main:func'],
+    },
+)