Define TrashPermissionError (#21)

send2trash/exceptions.py

@@ -0,0 +1,25 @@
+import errno
+from .compat import PY3
+
+if PY3:
+    _permission_error = PermissionError
+else:
+    _permission_error = OSError
+
+class TrashPermissionError(_permission_error):
+    """A permission error specific to a trash directory.
+
+    Raising this error indicates that permissions prevent us efficiently
+    trashing a file, although we might still have permission to delete it.
+    This is *not* used when permissions prevent removing the file itself:
+    that will be raised as a regular PermissionError (OSError on Python 2).
+
+    Application code that catches this may try to simply delete the file,
+    or prompt the user to decide, or (on Freedesktop platforms), move it to
+    'home trash' as a fallback. This last option probably involves copying the
+    data between partitions, devices, or network drives, so we don't do it as
+    a fallback.
+    """
+    def __init__(self, filename):
+        _permission_error.__init__(self, errno.EACCES, "Permission denied",
+                                   filename)