Pin urllib3 to less than 1.24 until transifex-client updates

requirements/edx/paver.in

@@ -18,6 +18,7 @@ psutil==1.2.1                       # Library for retrieving information on runn
 pymongo==2.9.1                      # via edx-opaque-keys
 python-memcached==1.48              # Python interface to the memcached memory cache daemon
 requests                            # Simple interface for making HTTP requests
+urllib3<1.24                        # transifex-client 0.13.5 requires urllib3<1.24, but requests will pull in urllib3==1.24 (https://github.com/transifex/transifex-client/pull/241/files)
 stevedore==1.10.0                   # via edx-opaque-keys
 urllib3==1.23                       # via requests
 watchdog                            # Used in paver watch_assets