[rubygems/rubygems] Show gemspec location when a Gem::MissingSpecError is raised while trying to activate a gem

https://github.com/rubygems/rubygems/commit/4da54a8e8b

lib/rubygems/specification.rb

@@ -1395,7 +1395,11 @@ class Gem::Specification < Gem::BasicSpecification
         raise e
       end
 
-      specs = spec_dep.to_specs
+      begin
+        specs = spec_dep.to_specs
+      rescue Gem::MissingSpecError => e
+        raise Gem::MissingSpecError.new(e.name, e.requirement, "at: #{self.spec_file}")
+      end
 
       if specs.size == 1
         specs.first.activate

test/rubygems/test_gem.rb

@@ -1275,6 +1275,7 @@ class TestGem < Gem::TestCase
     end
 
     assert_match %r{Could not find 'b' }, e.message
+    assert_match %r{at: #{a.spec_file}}, e.message
   end
 
   def test_self_try_activate_missing_prerelease