I am not sure if this is related just to archivebot.py or the general pywikibot. Posting here for awareness of the issue so it can get fixed before the feature is removed and bots get broken:
H:\MABot>pwb.py archivebot User:MABot/config -family:wikipedia -lang:sco -v -simulate
Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)]
Fetching template transclusions...
Found 1 wikipedia:sco processes running, including this one.
Processing [[sco:Wikipedia:Mercat Cross]]
WARNING: API warning (main): Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes. Use [[Special:ApiFeatureUsage]] to see usage of deprecated features by your application.
WARNING: API warning (revisions): Because "rvslots" was not specified, a legacy format has been used for the output. This format is deprecated, and in the future the new format will always be used.
59 Threads found on [[sco:Wikipedia:Mercat Cross]]
Looking for: {{User:MABot/config}} in [[sco:Wikipedia:Mercat Cross]]
Processing 59 threads
WARNING: API warning (main): Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes. Use [[Special:ApiFeatureUsage]] to see usage of deprecated features by your application.
WARNING: API warning (revisions): Because "rvslots" was not specified, a legacy format has been used for the output. This format is deprecated, and in the future the new format will always be used.
75 Threads found on [[sco:Wikipedia:Mercat Cross/Archive/2]]
Archiving 53 thread(s).
SIMULATION: edit action blocked.
Page [[Wikipedia:Mercat Cross/Archive/2]] saved without any changes.
Page [[Wikipedia:Mercat Cross/Archive/2]] saved
APISite("sco", "wikipedia").login(False) called when a previous login was in progress.
SIMULATION: edit action blocked.
Page [[Wikipedia:Mercat Cross]] saved without any changes.
Page [[Wikipedia:Mercat Cross]] saved
Dropped throttle(s).
Closing network session.
Network session closed.Thank you.