puppet module upgrade crashes

When upgrading a module on a private Forge the client crashes:

$ puppet module upgrade --module_repository=http://<customer>...com google-gstorage
Notice: Preparing to upgrade 'google-gstorage' ...
Notice: Found 'google-gstorage' (v0.2.0) in /home/nelsona/.puppetlabs/etc/code/modules ...
Error: undefined method `gsub' for false:FalseClass
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/forge.rb:240:in `decode_uri'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/forge.rb:110:in `fetch'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/module_tool/applications/upgrader.rb:93:in `run'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/face/module/upgrade.rb:73:in `block (3 levels) in <top (required)>'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/interface/action.rb+eval[wrapper]:264:in `upgrade'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/application/face_base.rb:247:in `main'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/application.rb:383:in `run_command'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/application.rb:375:in `block in run'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/util.rb:665:in `exit_on_fail'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/application.rb:375:in `run'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/util/command_line.rb:137:in `run'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/lib/puppet/util/command_line.rb:73:in `execute'
/home/nelsona/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/gems/puppet-5.4.0/bin/puppet:5:in `<top (required)>'
/home/nelsona/.rbenv/versions/2.5.0/bin/puppet:23:in `load'
/home/nelsona/.rbenv/versions/2.5.0/bin/puppet:23:in `<main>'