Make plugin loading more robust to errors

lib/vagrant.rb

@@ -172,6 +172,17 @@ module Vagrant
       require name
     rescue LoadError
       raise Errors::PluginLoadError, :plugin => name
+    rescue Exception => e
+      # Since this is a rare case, we create a one-time logger here
+      # in order to output the error
+      logger = Log4r::Logger.new("vagrant::root")
+      logger.error("Failed to load plugin: #{name}")
+      logger.error(" -- Error: #{e.inspect}")
+      logger.error(" -- Backtrace:")
+      logger.error(e.backtrace.join("\n"))
+
+      # And raise an error itself
+      raise Errors::PluginLoadFailed, :plugin => name
     end
   end
 end

lib/vagrant/environment.rb

@@ -610,7 +610,11 @@ module Vagrant
         data = JSON.parse(plugins_json_file.read)
         data["installed"].each do |plugin|
           @logger.info("Loading plugin from JSON: #{plugin}")
-          Vagrant.require_plugin(plugin)
+          begin
+            Vagrant.require_plugin(plugin)
+          rescue Errors::PluginLoadFailed => e
+            @ui.error(e.message)
+          end
         end
       end
     end

lib/vagrant/errors.rb

@@ -349,6 +349,10 @@ module Vagrant
       error_key(:plugin_load_error)
     end
 
+    class PluginLoadFailed < VagrantError
+      error_key(:plugin_load_failed)
+    end
+
     class SCPPermissionDenied < VagrantError
       status_code(82)
       error_key(:scp_permission_denied)

templates/locales/en.yml

@@ -178,6 +178,8 @@ en:
       plugin_load_error: |-
         The plugin "%{plugin}" could not be found. Please make sure that it is
         properly installed via `vagrant plugin`.
+      plugin_load_failed: |-
+        Failed to load the "%{plugin}" plugin. View logs for more details.
       port_collision_resume: |-
         This VM cannot be resumed, because the forwarded ports would collide with
         another running virtual machine. Normally, Vagrant will attempt to fix this