Add checks to Python scripts for version dependencies.

Signed-off-by: Eric S. Raymond <esr@thyrsus.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-p4.py

@@ -8,7 +8,13 @@
 # License: MIT <http://www.opensource.org/licenses/mit-license.php>
 #
 
-import optparse, sys, os, marshal, subprocess, shelve
+import sys
+if sys.hexversion < 0x02040000:
+    # The limiter is the subprocess module
+    sys.stderr.write("git-p4: requires Python 2.4 or later.\n")
+    sys.exit(1)
+
+import optparse, os, marshal, subprocess, shelve
 import tempfile, getopt, os.path, time, platform
 import re, shutil