BUG: Allow IOErrors when attempting to retrieve default client encoding.

doc/source/whatsnew/v0.23.2.txt

@@ -78,6 +78,7 @@ Bug Fixes
 
 - Bug in :func:`read_csv` that caused it to incorrectly raise an error when ``nrows=0``, ``low_memory=True``, and ``index_col`` was not ``None`` (:issue:`21141`)
 - Bug in :func:`json_normalize` when formatting the ``record_prefix`` with integer columns (:issue:`21536`)
+- Bug in :meth:`detect_client_encoding` where potential ``IOError`` goes unhandled when importing in a mod_wsgi process due to restricted access to stdout. (:issue:`21552`)
 -
 
 **Plotting**

pandas/io/formats/console.py

@@ -21,7 +21,7 @@ def detect_console_encoding():
     encoding = None
     try:
         encoding = sys.stdout.encoding or sys.stdin.encoding
-    except AttributeError:
+    except (AttributeError, IOError):
         pass
 
     # try again for something better

pandas/tests/io/formats/test_console.py

@@ -0,0 +1,51 @@
+import pytest
+from functools import partial
+
+from pandas.io.formats.console import detect_console_encoding, locale
+
+
+def mock_raises_exception(error=Exception):
+    raise error
+
+
+@pytest.mark.parametrize('empty,filled', [
+    ['stdin', 'stdout'],
+    ['stdout', 'stdin']
+])
+def test_detect_console_encoding_from_stdout_stdin(monkeypatch, empty, filled):
+    # Ensures that when sys.stdout.encoding or sys.stdin.encoding is used when
+    # they have values filled.
+    class MockEncoding(object):
+        def __init__(self, encoding):
+            super(MockEncoding, self).__init__()
+            self.encoding = encoding
+
+    monkeypatch.setattr('sys.{}'.format(empty), MockEncoding(''))
+    monkeypatch.setattr('sys.{}'.format(filled), MockEncoding(filled))
+    assert detect_console_encoding() == filled
+
+
+@pytest.mark.parametrize('stdEncoding', [
+    partial(mock_raises_exception, AttributeError),
+    partial(mock_raises_exception, IOError),
+    lambda: 'ascii'
+])
+def test_detect_console_encoding_fallback_to_locale(monkeypatch, stdEncoding):
+    monkeypatch.setattr('locale.getpreferredencoding', lambda: 'foo')
+    monkeypatch.setattr('sys.stdout', stdEncoding)
+    assert detect_console_encoding() == 'foo'
+
+
+@pytest.mark.parametrize('std,locale', [
+    ['ascii', 'ascii'],
+    ['ascii', mock_raises_exception],
+    [mock_raises_exception, 'ascii'],
+    [mock_raises_exception, mock_raises_exception]
+])
+def test_detect_console_encoding_fallback_to_default(monkeypatch, std, locale):
+    # When both the stdout/stdin encoding and locale preferred encoding checks
+    # fail (or return 'ascii', we should default to the sys default encoding.
+    monkeypatch.setattr('sys.stdout', std)
+    monkeypatch.setattr('locale.getpreferredencoding', locale)
+    monkeypatch.setattr('sys.getdefaultencoding', lambda: 'sysDefaultEncoding')
+    assert detect_console_encoding() == 'sysDefaultEncoding'