Add validation to args for shell provisioner

lib/vagrant/provisioners/shell.rb

@@ -39,6 +39,11 @@ module Vagrant
           if !upload_path
             errors.add(I18n.t("vagrant.provisioners.shell.upload_path_not_set"))
           end
+
+          # If there are args and its not a string, that is a problem
+          if args && !args.is_a?(String)
+            errors.add(I18n.t("vagrant.provisioners.shell.args_not_string"))
+          end
         end
       end
 

templates/locales/en.yml

@@ -509,6 +509,7 @@ en:
         running_puppetd: "Running Puppet agent..."
 
       shell:
+        args_not_string: "Shell provisioner `args` must be a string."
         path_and_inline_set: "Only one of `path` or `inline` may be set."
         no_path_or_inline: "One of `path` or `inline` must be set."
         path_invalid: "`path` for shell provisioner does not exist on the host system: %{path}"