BuildDoc shouldn't fail on Unicode paths.

Sub-classes of sphinx.setup_command.BuildDoc may choose to call
finalize_options in their run() method again for various reasons. However,
currently this fails with py2.7 because of http://bugs.python.org/issue19570.

Since it is unlikely that the upstream issue will be solved, a workaround is
to re-implement distutils' Command._ensure_stringlike to support Unicode
strings.

sphinx/setup_command.py

@@ -14,6 +14,7 @@
 
 import sys
 import os
+import types
 from StringIO import StringIO
 from distutils.cmd import Command
 
@@ -98,6 +99,19 @@ class BuildDoc(Command):
                     return root
         return None
 
+    # Overriding distutils' Command._ensure_stringlike which doesn't support
+    # unicode, causing finalize_options to fail if invoked again. Workaround
+    # for http://bugs.python.org/issue19570
+    def _ensure_stringlike(self, option, what, default=None):
+        val = getattr(self, option)
+        if val is None:
+            setattr(self, option, default)
+            return default
+        elif not isinstance(val, types.StringTypes):
+            raise DistutilsOptionError("'%s' must be a %s (got `%s`)"
+                                       % (option, what, val))
+        return val
+
     def finalize_options(self):
         if self.source_dir is None:
             self.source_dir = self._guess_source_dir()