Pretty error from Bundle.setup when gems are missing

lib/bundler.rb

@@ -69,16 +69,22 @@ def bundle_path
     def setup(*groups)
       return @setup if @setup
 
-      if groups.empty?
-        # Load all groups, but only once
-        @setup = load.setup
-      else
-        # Figure out which groups haven't been loaded yet
-        unloaded = groups - (@completed_groups || [])
-        # Record groups that are now loaded
-        @completed_groups = groups | (@completed_groups || [])
-        # Load any groups that are not yet loaded
-        unloaded.any? ? load.setup(*unloaded) : load
+      begin
+        if groups.empty?
+          # Load all groups, but only once
+          @setup = load.setup
+        else
+          # Figure out which groups haven't been loaded yet
+          unloaded = groups - (@completed_groups || [])
+          # Record groups that are now loaded
+          @completed_groups = groups | (@completed_groups || [])
+          # Load any groups that are not yet loaded
+          unloaded.any? ? load.setup(*unloaded) : load
+        end
+      rescue Bundler::GemNotFound => e
+        STDERR.puts e.message
+        STDERR.puts "Try running `bundle install`."
+        exit!
       end
     end
 

lib/bundler/runtime.rb

@@ -23,7 +23,7 @@ def setup(*groups)
       # Activate the specs
       specs.each do |spec|
         unless spec.loaded_from
-          raise GemNotFound, "#{spec.full_name} is not installed. Try running `bundle install`."
+          raise GemNotFound, "#{spec.full_name} is cached, but not installed."
         end
 
         Gem.loaded_specs[spec.name] = spec

spec/runtime/setup_spec.rb

@@ -145,17 +145,14 @@
         gem "rack"
       G
 
-      ruby <<-R
+      ruby <<-R, :expect_err => true
         require 'rubygems'
         require 'bundler'
-        begin
-          Bundler.setup
-        rescue Bundler::BundlerError => e
-          puts e.message
-        end
+        Bundler.setup
       R
 
-      out.should == "rack-1.0 is not installed. Try running `bundle install`."
+      err.should include("rack-1.0 is cached, but not installed")
+      err.should include("Try running `bundle install`.")
     end
   end
 
@@ -242,4 +239,17 @@
     err.should be_empty
   end
 
+  it "doesn't throw a backtrace when gems are missing" do
+    gemfile <<-G
+      source "file://#{gem_repo1}"
+      gem "imaginary"
+    G
+    run <<-R, :expect_err => true
+      Bundler.setup
+    R
+
+    err.should include"Could not find gem 'imaginary")
+    err.should include("Try running `bundle install`")
+  end
+
 end