There are multiple small issues so I'll report them all here:
xgettext does not seem to understand that P_ is an alias to ngettext. Maybe it's possible to configure it to understand but I think it's easier to use ngettext directly (note: I don't mean gettext.ngettext)
The string "Downloading %d files (%sB)..." should use ngettext for translations to be able to distinguish between "file" and "files".
The same for the string '%s available updates'; at the same place since update_count is probably an integer number it should be formatted using %d rather than %s.
There are multiple small issues so I'll report them all here:
xgettextdoes not seem to understand thatP_is an alias tongettext. Maybe it's possible to configure it to understand but I think it's easier to usengettextdirectly (note: I don't meangettext.ngettext)"Downloading %d files (%sB)..."should usengettextfor translations to be able to distinguish between "file" and "files".'%s available updates'; at the same place sinceupdate_countis probably an integer number it should be formatted using%drather than%s.