plugin attach, XEP-0363: progress id can now be specified:

progress id can be specified in options, using the "progress_id" option, this can be
more handy for frontends to keep track of attachments progresses.

sat/plugins/plugin_misc_file.py

@@ -48,7 +48,8 @@ This plugin manage the various ways of sending a file, and choose the best one."
 SENDING = D_("Please select a file to send to {peer}")
 SENDING_TITLE = D_("File sending")
 CONFIRM = D_(
-    '{peer} wants to send the file "{name}" to you:\n{desc}\n\nThe file has a size of {size_human}\n\nDo you accept ?'
+    '{peer} wants to send the file "{name}" to you:\n{desc}\n\nThe file has a size of '
+    '{size_human}\n\nDo you accept ?'
 )
 CONFIRM_TITLE = D_("Confirm file transfer")
 CONFIRM_OVERWRITE = D_("File {} already exists, are you sure you want to overwrite ?")
@@ -58,7 +59,7 @@ SECURITY_LIMIT = 30
 PROGRESS_ID_KEY = "progress_id"
 
 
-class FilePlugin(object):
+class FilePlugin:
     File = stream.SatFile
 
     def __init__(self, host):
@@ -99,7 +100,8 @@ class FilePlugin(object):
         @param filename(unicode, None): name to use, or None to find it from filepath
         @param file_desc(unicode, None): description of the file
         @param profile: %(doc_profile)s
-        @return (dict): action dictionary, with progress id in case of success, else xmlui message
+        @return (dict): action dictionary, with progress id in case of success, else
+            xmlui message
         """
         if not os.path.isfile(filepath):
             raise exceptions.DataError("The given path doesn't link to a file")