Fix encoding in config test and open configs in binary mode to warn for possible encoding errors

sphinx/config.py

@@ -165,7 +165,7 @@ class Config(object):
             try:
                 try:
                     os.chdir(dirname)
-                    f = open(config_file, 'U')
+                    f = open(config_file, 'Ub')
                     try:
                         code = compile(f.read(), config_file, 'exec')
                     finally:

tests/test_config.py

@@ -84,11 +84,12 @@ def test_extension_values(app):
 @with_tempdir
 def test_errors_warnings(dir):
     # test the error for syntax errors in the config file
-    write_file(dir / 'conf.py', 'project = \n')
+    write_file(dir / 'conf.py', u'project = \n', 'ascii')
     raises_msg(ConfigError, 'conf.py', Config, dir, 'conf.py', {}, None)
 
     # test the warning for bytestrings with non-ascii content
-    write_file(dir / 'conf.py', '# -*- coding: latin-1\nproject = "foo\xe4"\n')
+    write_file(dir / 'conf.py',
+               u'# -*- coding: latin-1\nproject = "fooä"\n', 'latin-1')
     cfg = Config(dir, 'conf.py', {}, None)
     warned = [False]
     def warn(msg):

tests/util.py

@@ -11,6 +11,7 @@ import sys
 import StringIO
 import tempfile
 import shutil
+from codecs import open
 
 try:
     from functools import wraps
@@ -191,8 +192,14 @@ def with_tempdir(func):
     return new_func
 
 
-def write_file(name, contents):
-    f = open(str(name), 'wb')
+def write_file(name, contents, encoding=None):
+    if encoding is None:
+        mode = 'wb'
+        if isinstance(contents, unicode):
+            contents = contents.encode('ascii')
+    else:
+        mode = 'w'
+    f = open(str(name), 'wb', encoding=encoding)
     f.write(contents)
     f.close()