Show digest mismatch in verify_download_integrity

Report "Expected <supplied digest>, got <file's digest>"
when verify_download_integrity sees a mismatch.  (It had
been, confusingly, reporting "Expected <file's digest>".)

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Library/Homebrew/formula.rb

@@ -353,7 +353,7 @@ private
     hash = fn.incremental_hash(hasher)
 
     if supplied and not supplied.empty?
-      raise "#{type} mismatch\nExpected: #{hash}\nArchive: #{fn}" unless supplied.upcase == hash.upcase
+      raise "#{type} mismatch\nExpected #{supplied}, got #{hash}\nArchive: #{fn}" unless supplied.upcase == hash.upcase
     else
       opoo "Cannot verify package integrity"
       puts "The formula did not provide a download checksum"