Made change_tracking_map_t save by wrapping access to the changed key set into a subscription
Removed debug message, because it was often triggered incorrectly.
Typo
Restructured change_tracking_map_t safety checks
Removed unused include
Merge branch 'next' into daniel_2702
merge of #2531 python 3
Remove 'OPAQUE' from error message

Fixes #972
Merge branch 'next' into daniel_2702
Merge pull request #2801 from gsathya/bug972

Remove 'OPAQUE' from error message. Submitted by @gsathya, reviewed by @danielmewes.
Merge branch 'next' into daniel_2777