Fix build dependencies, when the dependency is a string

CHANGELOG

@@ -16,6 +16,7 @@ v 8.6.0
   - Fix diff image view modes (2-up, swipe, onion skin) not working (Stan Hu)
   - Support Golang subpackage fetching (Stan Hu)
   - Bump Capybara gem to 2.6.2 (Stan Hu)
+  - Fix build dependencies, when the dependency is a string
   - New branch button appears on issues where applicable
   - Contributions to forked projects are included in calendar
   - Improve the formatting for the user page bio (Connor Shea)

lib/ci/gitlab_ci_yaml_processor.rb

@@ -242,9 +242,9 @@ module Ci
       stage_index = stages.index(job[:stage])
 
       job[:dependencies].each do |dependency|
-        raise ValidationError, "#{name} job: undefined dependency: #{dependency}" unless @jobs[dependency]
+        raise ValidationError, "#{name} job: undefined dependency: #{dependency}" unless @jobs[dependency.to_sym]
 
-        unless stages.index(@jobs[dependency][:stage]) < stage_index
+        unless stages.index(@jobs[dependency.to_sym][:stage]) < stage_index
           raise ValidationError, "#{name} job: dependency #{dependency} is not defined in prior stages"
         end
       end

spec/lib/ci/gitlab_ci_yaml_processor_spec.rb

@@ -492,19 +492,19 @@ module Ci
       end
 
       context 'dependencies to builds' do
-        let(:dependencies) { [:build1, :build2] }
+        let(:dependencies) { ['build1', 'build2'] }
 
         it { expect { subject }.to_not raise_error }
       end
 
       context 'undefined dependency' do
-        let(:dependencies) { [:undefined] }
+        let(:dependencies) { ['undefined'] }
 
         it { expect { subject }.to raise_error(GitlabCiYamlProcessor::ValidationError, 'test1 job: undefined dependency: undefined') }
       end
 
       context 'dependencies to deploy' do
-        let(:dependencies) { [:deploy] }
+        let(:dependencies) { ['deploy'] }
 
         it { expect { subject }.to raise_error(GitlabCiYamlProcessor::ValidationError, 'test1 job: dependency deploy is not defined in prior stages') }
       end