format.diff

Index: numba/type_inference/infer.py
===================================================================
--- numba/type_inference/infer.py       (revision 80685)
+++ numba/type_inference/infer.py       (revision 80686)
@@ -850,7 +850,11 @@
                 ["is_int", 'is_object', 'is_bool'])

         v1, v2 = node.left.variable, node.right.variable
-        promotion_type = self.promote(v1, v2)
+        # Handle string formatting with %
+        if isinstance(node.op, ast.Mod) and v1.type.is_c_string:
+            promotion_type = object_
+        else:
+            promotion_type = self.promote(v1, v2)

         if (v1.type.is_pointer or v2.type.is_pointer):
             self._verify_pointer_type(node, v1, v2)