Merge pull request #719 from scotje/maint_package_test_single_file

(MAINT) Allow use of RSPEC_PATTERN env var when running package tests

package-testing/Rakefile

@@ -82,7 +82,7 @@ namespace :acceptance do
   desc 'Run acceptance tests against a pdk package'
   RSpec::Core::RakeTask.new(:package) do |t|
     t.rspec_opts = ['--format documentation']
-    t.pattern = 'spec/package/**/*_spec.rb'
+    t.pattern = ENV['RSPEC_PATTERN'] || 'spec/package/**/*_spec.rb'
   end
   task package: [:hostgen]