Adding gmail oauth2 authentication

python-social-auth is an optional dependency

django_mailbox/transports/__init__.py

@@ -5,3 +5,4 @@ from django_mailbox.transports.mbox import MboxTransport
 from django_mailbox.transports.babyl import BabylTransport
 from django_mailbox.transports.mh import MHTransport
 from django_mailbox.transports.mmdf import MMDFTransport
+from django_mailbox.transports.gmail import GmailImapTransport

django_mailbox/transports/gmail.py

@@ -0,0 +1,49 @@
+from django_mailbox.transports.imap import ImapTransport
+
+class GmailImapTransport(ImapTransport):
+
+    def connect(self, username, password):
+        # Try to use oauth2 first.  It's much safer
+        try:
+            self._connect_oauth(username)
+        except (TypeError, ValueError), e:
+            print " Couldn't do oauth2", e
+            self.server = self.transport(self.hostname, self.port)
+            typ, msg = self.server.login(username, password)
+            self.server.select()
+
+    def _connect_oauth(self, username):
+        # username should be an email address that has already been authorized
+        # for gmail access
+        try:
+            from django_mailbox.google_utils import (
+                get_google_access_token,
+                fetch_user_info,
+                AccessTokenNotFound,
+            )
+        except ImportError:
+            raise ValueError(
+                "Install python-social-auth to use oauth2 auth for gmail"
+            )
+
+        access_token = None
+        while access_token is None:
+            try:
+                access_token = get_google_access_token(username)
+                google_email_address = fetch_user_info(username)['email']
+            except TypeError:
+                # This means that the google process took too long
+                # Trying again is the right thing to do
+                pass
+            except AccessTokenNotFound:
+                raise ValueError(
+                    "No Token available in python-social-auth for %s" % username
+                )
+
+        auth_string = 'user=%s\1auth=Bearer %s\1\1' % (
+            google_email_address,
+            access_token
+        )
+        self.server = self.transport(self.hostname, self.port)
+        self.server.authenticate('XOAUTH2', lambda x: auth_string)
+        self.server.select()