Some sites need to submit login information twice. Bellow is an example that worked with MWJournal. It submit the credentials 1st, then saves the outcome to the system temp location, then open it again and submit. In this case the 2nd page didn't have a form a fill so just submit. Some other sites may need more info to be filled then follow normal procedure to fill and submit.
raw = br.submit().read() # submit the form and read the 2nd login page
# save it to an htm temp file
with TemporaryFile(suffix='.htm') as fname:
with open(fname, 'wb') as f:
br.select_form(nr=0) # finds submit on the 2nd form
didwelogin = br.submit().read() # submit it and read the return html