docstring + travis

.travis.yml

@@ -15,7 +15,7 @@ install:
   - pip install -r requirements.txt
   - pip install -r tests/requirements.txt
 before_script: flake8
-script: pytest
+script: pytest --cov-report term-missing --cov=pytube
 sudo: required
 after_success:
   coveralls

pytube/cli.py

@@ -43,6 +43,11 @@ def main():
 
 
 def build_debug_report(url):
+    """Serialize the request data to json for offline debugging.
+
+    :param str url:
+        A valid YouTube watch URL.
+    """
     yt = YouTube(url)
     fp = os.path.join(
         os.getcwd(),