Steps to replicate the issue:

• pwb watchlist -new
• pwb watchlist -all

What happens?:
pwb watchlist -new retrieves all watch list from all sites found in user-config.py. After it pwb watchlist -all should retrieve it again but no watchlist is read.

Software version:
Pywikibot 3

I guess this never worked after rPWBCf6554bec433cad788e82fecd0ab84dabf457649b

Other information :
CachedRequest entries in the cache directory does not have a 'watchlistraw' key because we use a generator instead of a list:

• https://en.wikipedia.org/w/api.php?prop=info|imageinfo|categoryinfo&inprop=protection&iiprop=timestamp|user|comment|url|size|sha1|metadata&iilimit=max&list=watchlistraw&action=query&indexpageids=&continue=
• https://en.wikipedia.org/w/api.php?prop=info|imageinfo|categoryinfo&inprop=protection&iiprop=timestamp|user|comment|url|size|sha1|metadata&iilimit=max&generator=watchlistraw&action=query&indexpageids=&continue=