The HTTP digest authorization throws a ValueError when the authorization request sent by the server contains a name="value" pair, in which the value itself contains an = sign.
Fixing is simple. In ZSI/digest_auth.py, change line 93 from:
k,v = http_header[m.start():m.end()].split('=')
k,v = http_header[m.start():m.end()].split('=',1)
This limits the splitting to only the first = sign, leaving the value part of the string untouched.