Use type=path for pem_file, since that's a file (#1934)

cloud/google/gce_img.py

@@ -180,7 +180,7 @@ def main():
           state=dict(default='present', choices=['present', 'absent']),
           zone=dict(default='us-central1-a'),
           service_account_email=dict(),
-          pem_file=dict(),
+          pem_file=dict(type='path'),
           project_id=dict(),
           timeout=dict(type='int', default=180)
       )

cloud/google/gce_tag.py

@@ -188,7 +188,7 @@ def main():
             state=dict(default='present', choices=['present', 'absent']),
             zone=dict(default='us-central1-a'),
             service_account_email=dict(),
-            pem_file=dict(),
+            pem_file=dict(type='path'),
             project_id=dict(),
         )
     )