Fix double newline after Interrupt

Seems to be an issue with Ruby system() call doing a double fork.

Library/Homebrew/formula.rb

@@ -23,7 +23,7 @@
 #
 class ExecutionError <RuntimeError
   def initialize cmd, args=[]
-    super "#{cmd} #{args*' '}"
+    super "Failure while executing: #{cmd} #{args*' '}"
   end
 end
 class BuildError <ExecutionError

Library/Homebrew/utils.rb

@@ -64,11 +64,12 @@ end
 # Kernel.system but with exceptions
 def safe_system cmd, *args
   puts "#{cmd} #{args*' '}" if ARGV.verbose?
-
-  execd=Kernel.system cmd, *args
-  # somehow Ruby doesn't handle the CTRL-C from another process -- WTF!?
+  exec_success=Kernel.system cmd, *args
+  # some tools, eg. tar seem to confuse ruby and it doesn't propogate the
+  # CTRL-C interrupt to us too, so execution continues, but the exit code os
+  # still 2 so we raise our own interrupt
   raise Interrupt, cmd if $?.termsig == 2
-  raise ExecutionError.new(cmd, args) unless execd and $? == 0
+  raise ExecutionError.new(cmd, args) unless exec_success and $?.success?
 end
 
 def curl url, *args

bin/brew

@@ -210,7 +210,10 @@ rescue UsageError
 rescue SystemExit
   ohai "Kernel.exit" if ARGV.verbose?
 rescue Interrupt => e
-  puts # seemingly a newline is typical
+  # puts # seemingly a newline is typical
+  # Above is now commented out because the system() call forks and then forks
+  # again, so there are two of "us" so we get two exceptions raising and thus
+  # two newlines, which buggers up the shell. FIXME!
   exit 130
 rescue SystemCallError, RuntimeError => e
   if ARGV.debug?