Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/requests_oauthlib/compliance_fixes/fitbit.py

@@ -0,0 +1,25 @@
+"""
+The Fitbit API breaks from the OAuth2 RFC standard by returning an "errors"
+object list, rather than a single "error" string. This puts hooks in place so
+that oauthlib can process an error in the results from access token and refresh
+token responses. This is necessary to prevent getting the generic red herring
+MissingTokenError.
+"""
+
+from json import loads, dumps
+
+from oauthlib.common import to_unicode
+
+
+def fitbit_compliance_fix(session):
+    def _missing_error(r):
+        token = loads(r.text)
+        if "errors" in token:
+            # Set the error to the first one we have
+            token["error"] = token["errors"][0]["errorType"]
+        r._content = to_unicode(dumps(token)).encode("UTF-8")
+        return r
+
+    session.register_compliance_hook("access_token_response", _missing_error)
+    session.register_compliance_hook("refresh_token_response", _missing_error)
+    return session