test_datetimes.py: fix literal string (#60820)

* test_datetimes.py: fix literal string

* fix test

* fix repeated whitespace

* add whatsnew entry

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Author: haampie

doc/source/whatsnew/v3.0.0.rst

@@ -75,6 +75,7 @@ Other enhancements
 - Added half-year offset classes :class:`HalfYearBegin`, :class:`HalfYearEnd`, :class:`BHalfYearBegin` and :class:`BHalfYearEnd` (:issue:`60928`)
 - Errors occurring during SQL I/O will now throw a generic :class:`.DatabaseError` instead of the raw Exception type from the underlying driver manager library (:issue:`60748`)
 - Implemented :meth:`Series.str.isascii` and :meth:`Series.str.isascii` (:issue:`59091`)
+- Improved deprecation message for offset aliases (:issue:`60820`)
 - Multiplying two :class:`DateOffset` objects will now raise a ``TypeError`` instead of a ``RecursionError`` (:issue:`59442`)
 - Restore support for reading Stata 104-format and enable reading 103-format dta files (:issue:`58554`)
 - Support passing a :class:`Iterable[Hashable]` input to :meth:`DataFrame.drop_duplicates` (:issue:`59237`)

pandas/_libs/tslibs/offsets.pyx

@@ -5108,7 +5108,7 @@ def _warn_about_deprecated_aliases(name: str, is_period: bool) -> str:
         warnings.warn(
             f"\'{name}\' is deprecated and will be removed "
             f"in a future version, please use "
-            f"\'{c_PERIOD_AND_OFFSET_DEPR_FREQSTR.get(name)}\' "
+            f"\'{c_PERIOD_AND_OFFSET_DEPR_FREQSTR.get(name)}\'"
             f" instead.",
             FutureWarning,
             stacklevel=find_stack_level(),
@@ -5122,7 +5122,7 @@ def _warn_about_deprecated_aliases(name: str, is_period: bool) -> str:
             warnings.warn(
                 f"\'{name}\' is deprecated and will be removed "
                 f"in a future version, please use "
-                f"\'{_name}\' "
+                f"\'{_name}\'"
                 f" instead.",
                 FutureWarning,
                 stacklevel=find_stack_level(),

pandas/tests/arrays/test_datetimes.py

@@ -769,8 +769,10 @@ def test_date_range_frequency_M_Q_Y_raises(self, freq):
     @pytest.mark.parametrize("freq_depr", ["2MIN", "2nS", "2Us"])
     def test_date_range_uppercase_frequency_deprecated(self, freq_depr):
         # GH#9586, GH#54939
-        depr_msg = f"'{freq_depr[1:]}' is deprecated and will be removed in a "
-        f"future version. Please use '{freq_depr.lower()[1:]}' instead."
+        depr_msg = (
+            f"'{freq_depr[1:]}' is deprecated and will be removed in a "
+            f"future version, please use '{freq_depr.lower()[1:]}' instead."
+        )
 
         expected = pd.date_range("1/1/2000", periods=4, freq=freq_depr.lower())
         with tm.assert_produces_warning(FutureWarning, match=depr_msg):