adding ability for pre/post hooks to be run in same virtualenv if is .py

cookiecutter/hooks.py

@@ -48,6 +48,11 @@ def _run_hook(script_path, cwd='.'):
     absolute).
     If `cwd` is provided, the script will be run from that directory.
     '''
+
+    extension = os.path.splitext(script_path)[1]
+    if '.py' in extension:
+        script_path = [sys.executable, script_path]
+
     run_thru_shell = sys.platform.startswith('win')
     proc = subprocess.Popen(
         script_path,

tests/test_hooks.py

@@ -14,6 +14,16 @@
 
 from cookiecutter import hooks, utils
 
+PY3 = sys.version > '3'
+if PY3:
+    from unittest.mock import patch
+    input_str = 'builtins.input'
+else:
+    import __builtin__
+    from mock import patch
+    input_str = '__builtin__.raw_input'
+    from cStringIO import StringIO
+
 
 class TestFindHooks(unittest.TestCase):
 
@@ -71,6 +81,21 @@ def test_public_run_hook(self):
             hooks.run_hook('post_gen_project', tests_dir)
             self.assertTrue(os.path.isfile(os.path.join(tests_dir, 'shell_post.txt')))
 
+    def test_run_hook_python_executable(self):
+        with patch('subprocess.Popen') as subprocess:
+            hook_path = os.path.join(self.hooks_path, 'pre_gen_project.py')
+            hooks._run_hook(hook_path)
+            script_path = [sys.executable, hook_path]
+            run_thru_shell = sys.platform.startswith('win')
+            subprocess.assert_called_with(script_path, cwd='.', shell=run_thru_shell)
+
+    def test_run_hook_shell_executable(self):
+        with patch('subprocess.Popen') as subprocess:
+            hook_path = os.path.join(self.hooks_path, 'pre_gen_project.sh')
+            hooks._run_hook(hook_path)
+            script_path = hook_path
+            run_thru_shell = sys.platform.startswith('win')
+            subprocess.assert_called_with(script_path, cwd='.', shell=run_thru_shell)
 
 if __name__ == '__main__':
     unittest.main()