STYLE: Prohibit parsing exeption messages in try/except code flows

doc/source/reference/testing.rst

@@ -66,6 +66,7 @@ Exceptions and warnings
  errors.PyperclipException
  errors.PyperclipWindowsException
  errors.SpecificationError
+ errors.TimezoneDtypeMismatchError
  errors.UndefinedVariableError
  errors.UnsortedIndexError
  errors.UnsupportedFunctionCall

pandas/core/arrays/datetimes.py

@@ -45,7 +45,7 @@
  tzconversion,
 )
 from pandas._libs.tslibs.dtypes import abbrev_to_npy_unit
-from pandas.errors import PerformanceWarning
+from pandas.errors import PerformanceWarning, TimezoneDtypeMismatchError
 from pandas.util._exceptions import find_stack_level
 from pandas.util._validators import validate_inclusive
 
@@ -2830,7 +2830,7 @@ def _validate_tz_from_dtype(
  # We also need to check for the case where the user passed a
  # tz-naive dtype (i.e. datetime64[ns])
  if tz is not None and not timezones.tz_compare(tz, dtz):
- raise ValueError(
+ raise TimezoneDtypeMismatchError(
  "cannot supply both a tz and a "
  "timezone-naive dtype (i.e. datetime64[ns])"
  )

pandas/core/dtypes/cast.py

@@ -45,6 +45,7 @@
 from pandas.errors import (
  IntCastingNaNError,
  LossySetitemError,
+ TimezoneDtypeMismatchError,
 )
 
 from pandas.core.dtypes.common import (
@@ -1095,16 +1096,15 @@ def maybe_cast_to_datetime(
  else:
  try:
  dta = DatetimeArray._from_sequence(value, dtype=dtype)
- except ValueError as err:
- # We can give a Series-specific exception message.
- if "cannot supply both a tz and a timezone-naive dtype" in str(err):
- raise ValueError(
+ except TimezoneDtypeMismatchError as err:
+ raise ValueError(
  "Cannot convert timezone-aware data to "
  "timezone-naive dtype. Use "
  "pd.Series(values).dt.tz_localize(None) instead."
- ) from err
- raise
-
+ ) from err 
+ except ValueError:
+ raise 
+
  return dta
 
 

pandas/errors/__init__.py

@@ -1038,6 +1038,16 @@ class InvalidComparison(Exception):
  """
 
 
+class TimezoneDtypeMismatchError(ValueError):
+ """
+ Raised when both a separate tz and a tz-naive numpy datetime64 dtype are
+ supplied (e.g. tz is not None and dtype is datetime64[ns]).
+
+ Use case / message:
+ "cannot supply both a tz and a timezone-naive dtype (i.e. datetime64[ns])"
+ """
+
+
 __all__ = [
  "AbstractMethodError",
  "AttributeConflictWarning",
@@ -1081,6 +1091,7 @@ class InvalidComparison(Exception):
  "PyperclipException",
  "PyperclipWindowsException",
  "SpecificationError",
+ "TimezoneDtypeMismatchError",
  "UndefinedVariableError",
  "UnsortedIndexError",
  "UnsupportedFunctionCall",

pandas/tests/indexes/datetimes/test_constructors.py

@@ -19,6 +19,7 @@
  astype_overflowsafe,
  timezones,
 )
+from pandas.errors import TimezoneDtypeMismatchError
 
 import pandas as pd
 from pandas import (
@@ -709,7 +710,7 @@ def test_constructor_dtype_tz_mismatch_raises(self):
  "cannot supply both a tz and a timezone-naive dtype "
  r"\(i\.e\. datetime64\[ns\]\)"
  )
- with pytest.raises(ValueError, match=msg):
+ with pytest.raises(TimezoneDtypeMismatchError, match=msg):
  DatetimeIndex(idx, dtype="datetime64[ns]")
 
  # this is effectively trying to convert tz's