Fix rubocop warnings.

Author: fnando

.rubocop.yml

@@ -20,3 +20,6 @@ Style/PerlBackrefs:
 
 Gemspec/DevelopmentDependencies:
   Enabled: false
+
+Gemspec/AttributeAssignment:
+  Enabled: false

lib/guard/i18n-js.rb

@@ -77,7 +77,7 @@ def capture
       $stdout = original
     end
 
-    def validate_file(key, file)
+    def validate_file(key, file) #  rubocop:disable Naming/PredicateMethod
       return true if file && File.file?(file)
 
       error("#{key.inspect} must be a file")