Function simplib::caller failing in puppet 6

The test for the simplib::caller function is failing in puppet 6.

Thisis the error:

el7 18:38:17$ puppet apply --verbose --detailed-exitcodes /tmp/apply_manifest.pp.REnhn0
Info: Loading facts
Info: Loading facts
Info: Loading facts
Error: Evaluation Error: Error while evaluating a Function Call, OS 'CentOS 7.6.1810' is not supported at '/tmp/apply_manifest.pp.REnhn0:0' (file: /etc/puppetlabs/code/environments/production/modules/simplib/functions/module_metadata/assert.pp, line: 62, column: 9) on node el7.tasty.bacon

el7 executed in 2.89 seconds
Exited: 1
should return the correct location (FAILED - 1)
ssh connection to el7 has been terminated
removing temporary ssh-config files per-vagrant box
Destroying vagrant boxes
==> el7: Forcing shutdown of VM...
==> el7: Destroying VM and associated drives...

Failures:

1) simplib::caller function should return the correct location
Failure/Error: expect(results).to match(%r{#{host_modulepath}/testmod/manifests/init.pp}m)
expected "\e[0;32mInfo: Loading facts\e[0m\n\e[0;32mInfo: Loading facts\e[0m\n\e[0;32mInfo: Loading facts\e[0m...es/simplib/functions/module_metadata/assert.pp, line: 62, column: 9) on node el7.tasty.bacon\e[0m\n" to match /\/etc\/puppetlabs\/code\/environments\/production\/modules\/testmod\/manifests\/init.pp/m
Diff:
@@ -1,2 +1,5 @@
-/\/etc\/puppetlabs\/code\/environments\/production\/modules\/testmod\/manifests\/init.pp/m
+Info: Loading facts
+Info: Loading facts
+Info: Loading facts
+Error: Evaluation Error: Error while evaluating a Function Call, OS 'CentOS 7.6.1810' is not supported at '/tmp/apply_manifest.pp.REnhn0:0' (file: /etc/puppetlabs/code/environments/production/modules/simplib/functions/module_metadata/assert.pp, line: 62, column: 9) on node el7.tasty.bacon

1. ./spec/acceptance/suites/caller_function/caller_spec.rb:24:in `block (3 levels) in <top (required)>'

Finished in 27.92 seconds (files took 1 minute 46.97 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/acceptance/suites/caller_function/caller_spec.rb:21 # simplib::caller function should return the correct location