Be smarter about determining if plugin load failed

lib/vagrant.rb

@@ -169,9 +169,18 @@ module Vagrant
     # Attempt the normal require
     begin
       require name
-    rescue LoadError
-      raise Errors::PluginLoadError, :plugin => name
     rescue Exception => e
+      # If it is a LoadError we first try to see if it failed loading
+      # the top-level entrypoint. If so, then we report a different error.
+      if e.is_a?(LoadError)
+        # Parse the message in order to get what failed to load, and
+        # add some extra protection around if the message is different.
+        parts = e.to_s.split(" -- ", 2)
+        if parts.length == 2 && parts[1] == name
+          raise Errors::PluginLoadError, :plugin => name
+        end
+      end
+
       # 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")

test/unit/vagrant_test.rb

@@ -1,6 +1,8 @@
 require File.expand_path("../base", __FILE__)
 
 describe Vagrant do
+  include_context "unit"
+
   it "has the path to the source root" do
     described_class.source_root.should == Pathname.new(File.expand_path("../../../", __FILE__))
   end
@@ -39,5 +41,16 @@ describe Vagrant do
       expect { described_class.require_plugin("i_dont_exist") }.
         to raise_error(Vagrant::Errors::PluginLoadError)
     end
+
+    it "should raise an error if the loading failed in some other way" do
+      plugin_dir  = temporary_dir
+      plugin_path = plugin_dir.join("test.rb")
+      plugin_path.open("w") do |f|
+        f.write(%Q[require 'I_dont_exist'])
+      end
+
+      expect { described_class.require_plugin(plugin_path.to_s) }.
+        to raise_error(Vagrant::Errors::PluginLoadFailed)
+    end
   end
 end