Narrow mock for getfilesystemencoding

Rather than have the tests guess how many times
sys.getfilesystemencoding is going to be called, narrow the mock to
just the encodeutils module.

Change-Id: Ia52d4f380e4053e8962ce9dfc674e732baa167fb

oslo_utils/encodeutils.py

@@ -18,6 +18,12 @@ import sys
 import six
 
 
+# NOTE(blk-u): This provides a symbol that can be overridden just for this
+# module during testing. sys.getfilesystemencoding() is called by coverage so
+# mocking it globally caused the coverage job to fail.
+_getfilesystemencoding = sys.getfilesystemencoding
+
+
 def safe_decode(text, incoming=None, errors='strict'):
     """Decodes incoming text/bytes string using `incoming` if they're not
        already unicode.
@@ -169,7 +175,7 @@ def exception_to_unicode(exc):
 
     # Try the locale encoding, most error messages are encoded to this encoding
     # (ex: os.strerror(errno))
-    encoding = sys.getfilesystemencoding()
+    encoding = _getfilesystemencoding()
     try:
         return msg.decode(encoding)
     except UnicodeDecodeError:  # nosec

oslo_utils/tests/tests_encodeutils.py

@@ -15,8 +15,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import sys
-
 import mock
 from oslotest import base as test_base
 import six
@@ -137,18 +135,6 @@ class ExceptionToUnicodeTest(test_base.BaseTestCase):
             def __str__(self):
                 return self.value
 
-        def mock_getfilesystemencoding(test_value):
-            # NOTE(blk-u): sys.getfilesystemencoding is called by coverage
-            # while processing the functions/files called by the test so
-            # mocking getfilesystemencoding was causing the coverage job to
-            # fail since it doesn't know about koi8_r encoding, and the
-            # encoding might be incorrect when set in other cases. The
-            # workaround is to return the test value when it's called by
-            # oslo.utils and the original value when called later by coverage.
-            return mock.patch.object(
-                sys, 'getfilesystemencoding',
-                side_effect=[test_value, sys.getfilesystemencoding()])
-
         # On Python 3, an exception which returns bytes with is __str__()
         # method (like StrException(bytes)) is probably a bug, but it was not
         # harder to support this silly case in exception_to_unicode().
@@ -164,7 +150,8 @@ class ExceptionToUnicodeTest(test_base.BaseTestCase):
                          u'utf-8 \xe9\u20ac')
 
         # Force the locale encoding to ASCII to test the fallback
-        with mock_getfilesystemencoding('ascii'):
+        with mock.patch.object(encodeutils, '_getfilesystemencoding',
+                               return_value='ascii'):
             # Fallback: decode from ISO-8859-1
             exc = StrException(b'rawbytes \x80\xff')
             self.assertEqual(encodeutils.exception_to_unicode(exc),
@@ -181,7 +168,8 @@ class ExceptionToUnicodeTest(test_base.BaseTestCase):
                          u'unicode \xe9\u20ac')
 
         # Test the locale encoding
-        with mock_getfilesystemencoding('koi8_r'):
+        with mock.patch.object(encodeutils, '_getfilesystemencoding',
+                               return_value='koi8_r'):
             exc = StrException(b'\xf2\xd5\xd3\xd3\xcb\xc9\xca')
             # Decode from the locale encoding
             # (the message cannot be decoded from ASCII nor UTF-8)