llvm/test/BugPoint/compile-custom.ll.py: Make it py3-compatible. [PR19112]

FIXME: Get rid of invoking this.
I guess it wouldn't run on win32 due to lacking of shell support.

llvm-svn: 203740

llvm/test/BugPoint/compile-custom.ll.py

@@ -5,6 +5,6 @@ import sys
 # Currently any print-out from the custom tool is interpreted as a crash
 # (i.e. test is still interesting)
 
-print "Error: " + ' '.join(sys.argv[1:])
+print("Error: " + ' '.join(sys.argv[1:]))
 
 sys.exit(1)