CI: Check import is warning free (#24102)

Author: TomAugspurger

ci/code_checks.sh

@@ -153,8 +153,8 @@ fi
 ### CODE ###
 if [[ -z "$CHECK" || "$CHECK" == "code" ]]; then
 
-    MSG='Check for modules that pandas should not import' ; echo $MSG
-    python -c "
+    MSG='Check import. No warnings, and blacklist some optional dependencies' ; echo $MSG
+    python -W error -c "
 import sys
 import pandas
 

pandas/compat/__init__.py

@@ -139,6 +139,7 @@ def lfilter(*args, **kwargs):
     Hashable = collections.abc.Hashable
     Iterable = collections.abc.Iterable
     Mapping = collections.abc.Mapping
+    MutableMapping = collections.abc.MutableMapping
     Sequence = collections.abc.Sequence
     Sized = collections.abc.Sized
     Set = collections.abc.Set
@@ -200,6 +201,7 @@ def get_range_parameters(data):
     Hashable = collections.Hashable
     Iterable = collections.Iterable
     Mapping = collections.Mapping
+    MutableMapping = collections.MutableMapping
     Sequence = collections.Sequence
     Sized = collections.Sized
     Set = collections.Set

pandas/core/tools/datetimes.py

@@ -1,4 +1,3 @@
-from collections import MutableMapping
 from datetime import datetime, time
 from functools import partial
 
@@ -18,6 +17,7 @@
 from pandas.core.dtypes.generic import ABCDataFrame, ABCIndexClass, ABCSeries
 from pandas.core.dtypes.missing import notna
 
+from pandas import compat
 from pandas.core import algorithms
 
 
@@ -570,7 +570,7 @@ def to_datetime(arg, errors='raise', dayfirst=False, yearfirst=False,
             from pandas import Series
             values = convert_listlike(arg._values, True, format)
             result = Series(values, index=arg.index, name=arg.name)
-    elif isinstance(arg, (ABCDataFrame, MutableMapping)):
+    elif isinstance(arg, (ABCDataFrame, compat.MutableMapping)):
         result = _assemble_from_unit_mappings(arg, errors=errors)
     elif isinstance(arg, ABCIndexClass):
         cache_array = _maybe_cache(arg, format, cache, convert_listlike)