The default unittext tools will keep the space at the end of a line when wrapping. Ie like this:
msgstr "This is a long message that will be wrapped " "into multiple lines."
While polib (thanks to textwrap) will put those spaces at the beginning of the next line:
msgstr "This is a long message that will be wrapped" " into multiple lines."
Although both technically works, it means that when you run a script based on polib you get a massive diff. And then you run msgmerge to update from the updated pot-file, and the same thing happens again... :-)
I think it would be good if the default wrapping behavior was the same as the gettext tools degfault formatting.
The workaround is of course to run msgmerge after runnning your custom script, but before commiting. But it's still kinda annoying...