fix message and test case

Author: jgao8

pandas/_libs/tslibs/offsets.pyx

@@ -5203,9 +5203,9 @@ deprec_to_valid_alias = {
 def raise_invalid_freq(freq: str, extra_message: str | None = None) -> None:
     msg = f"Invalid frequency: {freq}."
     if extra_message is not None:
-        msg += " " + extra_message
+        msg += f" {extra_message}"
     if freq in deprec_to_valid_alias:
-        msg += " " + "Did you mean {deprec_to_valid_alias[name]}?"
+        msg += f" Did you mean {deprec_to_valid_alias[freq]}?"
     raise ValueError(msg)
 
 

pandas/tests/tseries/offsets/test_offsets.py

@@ -1158,7 +1158,7 @@ def test_offset_multiplication(
 
 
 def test_offset_deprecated_error():
-    with pytest.raises(ValueError, match=r"Did you mean h?"):
+    with pytest.raises(ValueError, match="Did you mean h"):
         date_range("2012-01-01", periods=3, freq="H")