Fix RuboCop violations

lib/cocoapods/external_sources/abstract_external_source.rb

@@ -165,7 +165,7 @@ module Pod
                  when String
                    path = "#{name}.podspec"
                    path << '.json' if json
-                   Specification.from_string(spec, path).tap {|s| s.defined_in_file = nil }
+                   Specification.from_string(spec, path).tap { |s| s.defined_in_file = nil }
                  when Specification
                    spec.dup
                  else

lib/cocoapods/sandbox.rb

@@ -264,7 +264,7 @@ module Pod
         spec = Specification.from_file(podspec)
         FileUtils.copy(podspec, output_path)
       when Specification
-        raise ArgumentError, "can only store Specification objects as json" unless json
+        raise ArgumentError, 'can only store Specification objects as json' unless json
         output_path.open('w') { |f| f.puts(podspec.to_pretty_json) }
         spec = podspec.dup
       else

spec/unit/installer_spec.rb

@@ -776,7 +776,6 @@ module Pod
         @installer = Installer.new(config.sandbox, podfile, lockfile)
         @installer.expects(:integrate_user_project)
         @installer.install!
-        pod_targets = @installer.aggregate_targets.map(&:pod_targets)
 
         ::SpecHelper.reset_config_instance
 
@@ -804,7 +803,6 @@ module Pod
         @installer = Installer.new(config.sandbox, podfile, lockfile)
         @installer.expects(:integrate_user_project)
         @installer.install!
-        pod_targets = @installer.aggregate_targets.map(&:pod_targets)
 
         ::SpecHelper.reset_config_instance