I'm getting the same error, using Python 2.7, on a different Linux system:
>>> urllib.urlretrieve('https://wa151.avayalive.com/WAAdminPanel/login.aspx?ReturnUrl=%2fWAAdminPanel%2fprivate%2fHome.aspx')
---------------------------------------------------------------------------
ContentTooShortError Traceback (most recent call last)
...
ContentTooShortError: retrieval incomplete: got only 11365 out of 13805 bytes
However, the same operation can be done (and actually works for me) using requests
:
>>> import requests
>>> r = requests.get('https://wa151.avayalive.com/WAAdminPanel/login.aspx?ReturnUrl=%2fWAAdminPanel%2fprivate%2fHome.aspx')
>>> with open(somefilepath, 'w') as f:
... f.write(r.text)
Is that working for you?