Add forgotten file from previous commit.

lib/spack/llnl/util/tty/color.py

@@ -158,6 +158,11 @@ def clen(string):
     return len(re.sub(r'\033[^m]*m', '', string))
 
 
+def cextra(string):
+    """"Length of extra color characters in a string"""
+    return len(''.join(re.findall(r'\033[^m]*m', string)))
+
+
 def cwrite(string, stream=sys.stdout, color=None):
     """Replace all color expressions in string with ANSI control
        codes and write the result to the stream.  If color is