(FM-8643) Ensure library requires fail usefully

.rubocop_todo.yml

@@ -1,19 +1,20 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2019-10-18 11:01:56 -0500 using RuboCop version 0.49.1.
+# on 2019-10-30 10:31:01 -0500 using RuboCop version 0.49.1.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
 
-# Offense count: 4
+# Offense count: 6
 GetText/DecorateFunctionMessage:
   Exclude:
     - 'lib/puppet/provider/exec/powershell.rb'
     - 'lib/puppet/provider/exec/pwsh.rb'
     - 'spec/spec_helper_acceptance.rb'
 
-# Offense count: 1
+# Offense count: 3
 GetText/DecorateString:
   Exclude:
     - 'lib/puppet/provider/exec/powershell.rb'
+    - 'lib/puppet/provider/exec/pwsh.rb'

lib/puppet/provider/exec/powershell.rb

@@ -1,5 +1,9 @@
 require 'puppet/provider/exec'
-require 'ruby-pwsh'
+begin
+  require 'ruby-pwsh'
+rescue LoadError
+  raise 'Could not load the "ruby-pwsh" library; is the dependency module puppetlabs-pwshlib installed in this environment?'
+end
 
 Puppet::Type.type(:exec).provide :powershell, :parent => Puppet::Provider::Exec do
   confine :operatingsystem => :windows

lib/puppet/provider/exec/pwsh.rb

@@ -1,5 +1,9 @@
 require 'puppet/provider/exec'
-require 'ruby-pwsh'
+begin
+  require 'ruby-pwsh'
+rescue LoadError
+  raise 'Could not load the "ruby-pwsh" library; is the dependency module puppetlabs-pwshlib installed in this environment?'
+end
 
 Puppet::Type.type(:exec).provide :pwsh, :parent => Puppet::Provider::Exec do
   desc <<-EOT