Support unicode filenames

Python2 encodes commandline parameters based on the default system encoding.
We must explicitly decode this to unicode.
Python3 uses unicode filenames by default, so no action needed.

trovebox/main.py

@@ -123,7 +123,14 @@ def extract_files(params):
     updated_params = {}
     for name in params:
         if name == "photo" and params[name].startswith("@"):
-            files[name] = open(os.path.expanduser(params[name][1:]), 'rb')
+            filename = params[name][1:]
+
+            # Python2 uses encoded commandline parameters.
+            # Decode to Unicode if necessary.
+            if isinstance(filename, bytes):
+                filename = filename.decode(sys.getfilesystemencoding())
+
+            files[name] = open(os.path.expanduser(filename), 'rb')
         else:
             updated_params[name] = params[name]