$ python2 -c "from launchpadlib import launchpad as lp; lp.Launchpad.login_with('foobar', credentials_file='foobar.txt')"
The authorization page:
 (https://staging.launchpad.net/+authorize-token?oauth_token=Jn9q25rknkKcN5Q3Pnmb&allow_permission=DESKTOP_INTEGRATION)
should be opening in your browser. Use your browser to authorize
this program to access Launchpad on your behalf.
Waiting to hear from Launchpad about your decision...
[2864:2907:0815/112249:ERROR:nss_util.cc(842)] After loading Root Certs, loaded==false: NSS error code: -8018
Created new window in existing browser session.
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "launchpadlib/launchpad.py", line 549, in login_with
    credential_save_failed, version)
  File "launchpadlib/launchpad.py", line 356, in _authorize_token_and_login
    credentials = authorization_engine(credentials, credential_store)
  File "launchpadlib/credentials.py", line 546, in __call__
    self.make_end_user_authorize_token(credentials, request_token_string)
  File "launchpadlib/credentials.py", line 661, in make_end_user_authorize_token
    self.web_root)
  File "launchpadlib/credentials.py", line 232, in exchange_request_token_for_access_token
    self.access_token = AccessToken.from_string(content)
  File "launchpadlib/credentials.py", line 249, in from_string
    if isinstance(content, bytes):
UnboundLocalError: local variable 'content' referenced before assignment