When using the bash source command command-not-found behaves as if it was interactive

When using the bash "source" command from an interactive shell it is
 1) very slow
 2) pressing Control-C repeatedly reports python errors like:
Failed to import the site module
Traceback (most recent call last):
  File "/usr/lib/python3.4/site.py", line 586, in <module>
    main()

This has been verified on Ubuntu 14 and 18.

This can be reproduced by sourcing a file with about 50 lines of a word which is not found.
For example:
  for i in $(seq 50); do echo lss ; done > bad.sh
  source ./bad.sh

output will show something like:
 No command 'lss' found, did you mean:
 Command 'ss' from package 'iproute2' (main)
 Command 'ls' from package 'coreutils' (main)
...

Additionally, if you try to press ^C repeatedly you will get the errors from Python.

I would have expected the command-not-found to behave as if it was in a non interactive shell and not provide
interactive feedback, and not slow down the execution by doing a search that significantly slows the executions.

Thanks,
-tom