Convert codebase for python3 usage

modelviz.py

@@ -33,7 +33,7 @@ import getopt, sys
 from django.core.management import setup_environ
 
 try:
-    import settings
+    from . import settings
 except ImportError:
     pass
 else:
@@ -180,22 +180,22 @@ def main():
     try:
         opts, args = getopt.getopt(sys.argv[1:], "hd",
                     ["help", "disable_fields"])
-    except getopt.GetoptError, error:
-        print __doc__
+    except getopt.GetoptError as error:
+        print(__doc__)
         sys.exit(error)
     else:
         if not args:
-            print __doc__
+            print(__doc__)
             sys.exit()
 
     kwargs = {}
     for opt, arg in opts:
         if opt in ("-h", "--help"):
-            print __doc__
+            print(__doc__)
             sys.exit()
         if opt in ("-d", "--disable_fields"):
             kwargs['disable_fields'] = True
-    print generate_dot(args, **kwargs)
+    print(generate_dot(args, **kwargs))
 
 if __name__ == "__main__":
     main()