Adding depracated warning for units M and Y

Author: ryankarlos

pandas/core/tools/timedeltas.py

@@ -14,6 +14,7 @@
  is_timedelta64_dtype,
  is_list_like)
 from pandas.core.dtypes.generic import ABCSeries, ABCIndexClass
+import warnings
 
 
 def to_timedelta(arg, unit='ns', box=True, errors='raise'):
@@ -130,6 +131,9 @@ def to_timedelta(arg, unit='ns', box=True, errors='raise'):
 def _validate_timedelta_unit(arg):
  """ provide validation / translation for timedelta short units """
  try:
+ if arg == 'Y' or arg == 'y' or arg == 'M':
+ warnings.warn("Month and year units are deprecated.",
+ FutureWarning, stacklevel=2)
  return _unit_map[arg]
  except (KeyError, TypeError):
  if arg is None: