[DRE-maint] Bug#956600: ruby-coveralls: ftbfs with ruby-thor from experimental - Could not find 'thor' (~> 0.19.4) - did find: [thor-0.20.3] (Gem::MissingSpecVersionError)

[Pirate Praveen]

Package: ruby-coveralls
Version: 0.8.22-3
Severity: important

GEM_PATH= ruby2.7 -e gem\ \"coveralls\"
/usr/lib/ruby/2.7.0/rubygems/dependency.rb:313:in `to_specs': Could not 
find 'thor' (~> 0.19.4) - did find: [thor-0.20.3] 
(Gem::MissingSpecVersionError)

ruby-thor 0.20.3 will be uploaded to unstable soon so please fix this 
failure.