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

doc/source/whatsnew/v0.24.0.txt

@@ -384,7 +384,7 @@ I/O
 
 - :func:`read_html()` no longer ignores all-whitespace ``<tr>`` within ``<thead>`` when considering the ``skiprows`` and ``header`` arguments. Previously, users had to decrease their ``header`` and ``skiprows`` values on such tables to work around the issue. (:issue:`21641`)
 - :func:`read_excel()` will correctly show the deprecation warning for previously deprecated ``sheetname`` (:issue:`17994`)
--
+- 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 +1,71 @@
+import pytest
+
+from pandas.io.formats.console import detect_console_encoding
+
+
+class MockEncoding(object):  # TODO(py27): replace with mock
+    """
+    Used to add a side effect when accessing the 'encoding' property. If the
+    side effect is a str in nature, the value will be returned. Otherwise, the
+    side effect should be an exception that will be raised.
+    """
+    def __init__(self, encoding):
+        super(MockEncoding, self).__init__()
+        self.val = encoding
+
+    @property
+    def encoding(self):
+        return raise_or_return(self.val)
+
+
+def raise_or_return(val):
+    if isinstance(val, str):
+        return val
+    else:
+        raise val
+
+
+@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.
+    # GH 21552
+    with monkeypatch.context() as context:
+        context.setattr('sys.{}'.format(empty), MockEncoding(''))
+        context.setattr('sys.{}'.format(filled), MockEncoding(filled))
+        assert detect_console_encoding() == filled
+
+
+@pytest.mark.parametrize('encoding', [
+    MockEncoding(AttributeError),
+    MockEncoding(IOError),
+    MockEncoding('ascii')
+])
+def test_detect_console_encoding_fallback_to_locale(monkeypatch, encoding):
+    # GH 21552
+    with monkeypatch.context() as context:
+        context.setattr('locale.getpreferredencoding', lambda: 'foo')
+        context.setattr('sys.stdout', encoding)
+        assert detect_console_encoding() == 'foo'
+
+
+@pytest.mark.parametrize('std,locale', [
+    [MockEncoding('ascii'), lambda: 'ascii'],
+    [MockEncoding('ascii'), lambda: raise_or_return(Exception)],
+    [MockEncoding(AttributeError), lambda: 'ascii'],
+    [MockEncoding(AttributeError), lambda: raise_or_return(Exception)],
+    [MockEncoding(IOError), lambda: 'ascii'],
+    [MockEncoding(IOError), lambda: raise_or_return(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.
+    # GH 21552
+    with monkeypatch.context() as context:
+        context.setattr('locale.getpreferredencoding', locale)
+        context.setattr('sys.stdout', std)
+        context.setattr('sys.getdefaultencoding', lambda: 'sysDefaultEncoding')
+        assert detect_console_encoding() == 'sysDefaultEncoding'