Add support for check for the latest released version of Mayan.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/common/exceptions.py

@@ -0,0 +1,16 @@
+from __future__ import unicode_literals
+
+
+class BaseCommonException(Exception):
+    """
+    Base exception for the common app
+    """
+    pass
+
+
+class NotLatestVersion(BaseCommonException):
+    """
+    The installed version is not the latest available version
+    """
+    def __init__(self, upstream_version):
+        self.upstream_version = upstream_version