All hell breaks loose when unicode is passed as the second argument to urllib.quote in Python 2:

>>> import urllib
>>> urllib.quote('\xce\x91', u'')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/urllib.py", line 1292, in quote
    if not s.rstrip(safe):
UnicodeDecodeError: 'ascii' codec can't decode byte 0xce in position 0: ordinal not in range(128)

This on its own wouldn't be that bad - just another Python 2 unicode wonkiness.  However, coupled with caching done by the quote function (quoters are cached based on the second parameter, and u'' == ''), it means that a random preceding call to quote from an entirely different place in the application can break your code:

$ python2
Python 2.7.9 (default, Dec 11 2014, 04:42:00)
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import urllib
>>> urllib.quote('\xce\x91', '')
'%CE%91'
>>>


$ python2
Python 2.7.9 (default, Dec 11 2014, 04:42:00)
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import urllib
>>> urllib.quote('a', u'')
'a'
>>> urllib.quote('\xce\x91', '')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/urllib.py", line 1292, in quote
    if not s.rstrip(safe):
UnicodeDecodeError: 'ascii' codec can't decode byte 0xce in position 0: ordinal not in range(128)

Good luck debugging that.

So, one of two things needs to happen:

- a TypeError when unicode is passed as the second parameter, or
- a cast of the second parameter to str