Introduce pyupgrade

Closes #1742 (closed)

Introducing pyupgrade.

Again, I've made one commit per rule.

arkindex/project/fields.py

@@ -120,7 +120,7 @@ class LastItemTransform(Transform):
 
     def as_sql(self, compiler, connection):
         lhs, params = compiler.compile(self.lhs)
-        return "%s[array_length(%s, 1)]" % (lhs, lhs), params
+        return f"{lhs}[array_length({lhs}, 1)]", params
 
     @property
     def output_field(self):