ERR: include original error message for missing required dependencies

pandas/__init__.py

@@ -5,21 +5,21 @@
 # Let users know if they're missing any of our hard dependencies
 hard_dependencies = ("numpy", "pytz", "dateutil")
 missing_dependencies = []
-msg = None
-e = None
 
 for dependency in hard_dependencies:
     try:
         __import__(dependency)
     except ImportError as e:
         missing_dependencies.append((dependency, e))
 
+msg = None
+ex = None
 if missing_dependencies:
     msg = "Unable to import required dependencies:"
-    for dependency, e in missing_dependencies:
-        msg += "\n{0}: {1}".format(dependency, str(e))
+    for dependency, ex in missing_dependencies:
+        msg += "\n{0}: {1}".format(dependency, str(ex))
     raise ImportError(msg)
-del hard_dependencies, dependency, missing_dependencies, e, msg
+del hard_dependencies, dependency, missing_dependencies, ex, msg
 
 # numpy compat
 from pandas.compat.numpy import (

pandas/tests/test_base.py

@@ -1,9 +1,9 @@
+import builtins
 from datetime import datetime, timedelta
 from importlib import reload
 from io import StringIO
 import re
 import sys
-from unittest.mock import patch
 
 import numpy as np
 import pytest
@@ -1345,7 +1345,7 @@ def test_to_numpy_dtype(as_series):
     tm.assert_numpy_array_equal(result, expected)
 
 
-def test_missing_required_dependency():
+def test_missing_required_dependency(monkeypatch):
     original_import = __import__
 
     def mock_import_fail(name, *args, **kwargs):
@@ -1365,8 +1365,8 @@ def mock_import_fail(name, *args, **kwargs):
         "\ndateutil: cannot import name some_other_dependency"
     )
 
-    with patch("builtins.__import__") as mock_import:
-        mock_import.side_effect = mock_import_fail
+    with monkeypatch.context() as m:
+        m.setattr(builtins, "__import__", mock_import_fail)
         with pytest.raises(ImportError, match=expected_msg):
             reload(pd)