Login with Python-Mechanize results in UnicodeEncodeError

I am trying to login to partnernet.amazon.de ( german amazon affiliate program).

This is my code:

import cookielib 
import mechanize 

# Browser 
br = mechanize.Browser()

# Enable cookie support for urllib2 
cookiejar = cookielib.LWPCookieJar() 
br.set_cookiejar( cookiejar ) 

# Broser options 
br.set_handle_equiv(True) 
br.set_handle_gzip(True) 
br.set_handle_redirect(True) 
br.set_handle_referer(True) 
br.set_handle_robots(False) 

#
br.set_handle_refresh( mechanize._http.HTTPRefreshProcessor(), max_time = 1 ) 

br.addheaders = [ ( 'User-agent', 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36' ) ]

# authenticate 
br.open('https://partnernet.amazon.de/gp/associates/join/landing/')
br.select_form(name="sign_in")
br['username'] = 'username'
br['password'] = 'password'
res = br.submit() # error occurs here

print "Success!\n"

      

        
        
        
      

    

Failure script: UnicodeEncodeError: 'ascii' codec can't encode character u'\xc5' in position 0: ordinal not in range(128)

.

The error occurs because of this parameter of the form sign_in.

`[(u'__mk_de_DE', u'\xc5M\xc5\u017d\xd5\xd1'), ...] # ÅMÅŽÕÑ`

      

        
        
        
      

    

So I know this is a coding problem and where it is going. I can't figure out how / where to set the correct encoding to prevent this error.

Update: The bug is reproducible with the above code. You don't need to have real login details.