Always give hashlib.sha1 and friends bytes.

This fixes an experienced bug where you couldn't subscribe to a stream
with non-ASCII characters (failing with a UnicodeEncodeError), as well
as many other potential bugs.

(imported from commit f084a4b4b597b85935655097a7b5a163811c4d71)

zephyr/lib/cache.py

@@ -1,9 +1,10 @@
 from functools import wraps
-import hashlib
 
 from django.core.cache import cache as djcache
 from django.core.cache import get_cache
 
+from utils import make_safe_digest
+
 def cache_with_key(keyfunc, cache_name=None, timeout=None):
     """Decorator which applies Django caching to a function.
 
@@ -56,7 +57,10 @@ def message_cache_key(message_id):
     return "message:%d" % (message_id,)
 
 def user_profile_by_email_cache_key(email):
-    return 'user_profile_by_email:%s' % (hashlib.sha1(email).hexdigest(),)
+    # See the comment in zephyr/lib/avatar.py:gravatar_hash for why we
+    # are proactively encoding email addresses even though they will
+    # with high likelihood be ASCII-only for the foreseeable future.
+    return 'user_profile_by_email:%s' % (make_safe_digest(email),)
 
 def user_profile_by_user_cache_key(user_id):
     return 'user_profile_by_user_id:%d' % (user_id,)