acl/xattr: Be less strict about unknown platforms

Closes #239

CHANGES

@@ -6,7 +6,8 @@ Here you can see the full list of changes between each Attic release.
 Version 0.15
 ------------
 
-(feature release, released on X)
+(bugfix release, released on Apr 15, 2015)
+- xattr: Be less strict about unknown/unsupported platforms (#239)
 - Reduce repository listing memory usage (#163).
 - Fix BrokenPipeError for remote repositories (#233)
 - Fix incorrect behavior with two character directory names (#265, #268)

attic/platform.py

@@ -9,9 +9,9 @@ elif platform == 'FreeBSD':
 elif platform == 'Darwin':
     from attic.platform_darwin import acl_get, acl_set, API_VERSION
 else:
-    API_VERSION = 1
+    API_VERSION = 2
 
-    def acl_get(path, item, numeric_owner=False):
+    def acl_get(path, item, st, numeric_owner=False):
         pass
     def acl_set(path, item, numeric_owner=False):
         pass

attic/xattr.py

@@ -248,4 +248,11 @@ elif sys.platform.startswith('freebsd'):
         _check(func(path, EXTATTR_NAMESPACE_USER, name, value, len(value) if value else 0), path)
 
 else:
-    raise Exception('Unsupported platform: %s' % sys.platform)
+    def listxattr(path, *, follow_symlinks=True):
+        return []
+
+    def getxattr(path, name, *, follow_symlinks=True):
+        pass
+
+    def setxattr(path, name, value, *, follow_symlinks=True):
+        pass