Tweak brew server - fixes Homebrew/homebrew#2191

Library/Contributions/examples/brew-server

@@ -4,17 +4,24 @@
 # Note: this external command is ruby, but set up as a shell script, so that it gets exec'd.
 # This is required for sinatra's run-loop to take over.
 
-puts "View our tasting menu at http://localhost:4567/\nUse \"Control-C\" to exit.\n\n"
 $:.unshift(ENV['HOMEBREW_LIBRARY_PATH'])
 
-require 'rubygems'
-require 'sinatra'
-
-require 'cgi'
-
 require 'global'
 require 'formula'
 
+require 'rubygems'
+
+begin
+  require 'sinatra'
+rescue LoadError
+  onoe 'Sinatra required but not found'
+  puts 'To install: gem install sinatra'
+  exit 1
+end
+
+require 'cgi'
+
+
 def link_to_formula name
   "<a href=\"/formula/#{CGI.escape(name)}\">#{name}</a>"
 end
@@ -145,7 +152,7 @@ get '/formula/:name' do
   end
 
   used_by = Formula.all.select{|ff| ff.deps.include?(klass.name)}.map{|f| f.name}.flatten.uniq.sort
-  unless used_by == nil
+  unless used_by.empty?
     s << <<-HTML
             <dt>Used by</td>
     HTML
@@ -164,3 +171,5 @@ get '/formula/:name' do
 
   return s
 end
+
+puts "View our tasting menu at http://localhost:4567/\nUse \"Control-C\" to exit.\n\n"