fix and add test case

Author: jack-tutor

mypy/checkstrformat.py

@@ -1073,7 +1073,7 @@ def conversion_type(
                 return UnionType(
                     [self.named_type("builtins.int"), self.named_type("builtins.str")]
                 )
-        elif p in ["<", ">", "=", "^"]:
+        elif p.startswith(("<", ">", "=", "^")):
             return UnionType(
                 [
                     self.named_type("builtins.int"), 

test-data/unit/check-errorcodes.test

@@ -645,6 +645,7 @@ def g() -> int:
 
 '{}'.format(b'abc')  # E: If x = b'abc' then f"{x}" or "{}".format(x) produces "b'abc'", not "abc". If this is desired behavior, use f"{x!r}" or "{!r}".format(x). Otherwise, decode the bytes  [str-bytes-safe]
 '%s' % b'abc'  # E: If x = b'abc' then "%s" % x produces "b'abc'", not "abc". If this is desired behavior use "%r" % x. Otherwise, decode the bytes  [str-bytes-safe]
+'{:>2}'.format(None)
 [builtins fixtures/primitives.pyi]
 [typing fixtures/typing-medium.pyi]