dev-python/feedparser-5.2.1 is not fully python-3.7 compatible. It throws runtime errors "generator raised StopIteration" as a side effect of PEP479.
This causes e.g. rss2email to fail
$ r2e run
2020-05-20 17:50:35,989 [ERROR] error while running time limited function: generator raised StopIteration
2020-05-20 17:50:35,989 [ERROR] cause: generator raised StopIteration
Patch is available upstream:
Created attachment 640576 [details, diff]
backported upstream patch for feedparser 5.2.1
Upstream patch is not compatible to 5.2.1. I have back ported the patch.