Use re instead of regex.

Don't rewrite the file in place.
(Reported by Andy Dustman.)

Tools/scripts/fixps.py

-#! /usr/bin/env python
+#!/usr/bin/env python
 
 # Fix Python script(s) to reference the interpreter via /usr/bin/env python.
+# Warning: this overwrites the file without making a backup.
 
 import sys
-import regex
-import regsub
+import re
 
 
 def main():
 	for file in sys.argv[1:]:
 		try:
-			f = open(file, 'r+')
-		except IOError:
-			print file, ': can\'t open for update'
+			f = open(file, 'r')
+		except IOError, msg:
+			print file, ': can\'t open :', msg
 			continue
 		line = f.readline()
-		if regex.match('^#! */usr/local/bin/python', line) < 0:
+		if not re.match('^#! */usr/local/bin/python', line):
 			print file, ': not a /usr/local/bin/python script'
 			f.close()
 			continue
 		rest = f.read()
-		line = regsub.sub('/usr/local/bin/python',
-				  '/usr/bin/env python', line)
+		f.close()
+		line = re.sub('/usr/local/bin/python',
+			      '/usr/bin/env python', line)
 		print file, ':', `line`
-		f.seek(0)
+		f = open(file, "w")
 		f.write(line)
 		f.write(rest)
 		f.close()