Remove django-shorturls with my own implementation, since it's incompatible with Django 2 and unmaintained

lemonshort/convert.py

@@ -0,0 +1,15 @@
+from baseconv import BaseConverter
+from string import ascii_lowercase, ascii_uppercase
+
+# We have to create this collection ourselves because we want uppercase then
+# lowercase, and string.ascii_letters is lowercase then uppercase.
+chars = ascii_uppercase + ascii_lowercase
+conv = BaseConverter(chars)
+
+
+def abc_to_id(abc):
+    return int(conv.decode(abc))
+
+
+def id_to_abc(id):
+    return conv.encode(id)