Fix to make ConfigOpts no longer obscure IOErrors

This changes ConfigParser._parse_file such that it no longer interprets
all IOErrors as 'No such file or directory', and instead allows these
errors to propagate normally. The current behavior with respect to
ConfigOpts does not change for IOErrors indicating 'No such file' or
'Permission denied'.

Also added a test to exercise the case where IOErrors are reraised. The
'No such file' case is already covered by existing tests.

Change-Id: I10e4e5965212737a19f4f17153143f62b5c0c83e
Closes-Bug: #1244674

oslo/config/cfg.py

@@ -263,6 +263,7 @@ command line arguments using the SubCommandOpt class:
 import argparse
 import collections
 import copy
+import errno
 import functools
 import glob
 import itertools
@@ -1275,9 +1276,11 @@ class ConfigParser(iniparser.BaseParser):
             parser.parse()
         except iniparser.ParseError as pe:
             raise ConfigFileParseError(pe.filename, str(pe))
-        except IOError:
-            namespace._file_not_found(config_file)
-            return
+        except IOError as err:
+            if err.errno in (errno.ENOENT, errno.EACCES):
+                namespace._file_not_found(config_file)
+                return
+            raise
 
         namespace.add_parsed_config_file(sections, normalized)
 

test-requirements.txt

@@ -15,3 +15,6 @@ coverage>=3.6
 # this is required for the docs build jobs
 sphinx>=1.1.2
 oslo.sphinx
+
+# mocking framework
+mock>=1.0

tests/test_cfg.py

@@ -15,12 +15,14 @@
 #    under the License.
 
 import argparse
+import errno
 import os
 import shutil
 import sys
 import tempfile
 
 import fixtures
+import mock
 import six
 from six import moves
 import testscenarios
@@ -2517,6 +2519,17 @@ class ConfigParserTestCase(BaseTestCase):
             parser = cfg.ConfigParser(tmpfile.name, {})
             self.assertRaises(cfg.ParseError, parser.parse)
 
+    def test__parse_file_ioerror(self):
+        # Test that IOErrors (other than 'No such file or directory')
+        # are propagated.
+        filename = 'fake'
+        namespace = mock.Mock()
+        with mock.patch('oslo.config.cfg.ConfigParser.parse') as parse:
+            parse.side_effect = IOError(errno.EMFILE, filename,
+                                        'Too many open files')
+            self.assertRaises(IOError, cfg.ConfigParser._parse_file, filename,
+                              namespace)
+
 
 class MultiConfigParserTestCase(BaseTestCase):