tools/check: update python version check

Python 2.3 is the minimal version according to the README.
Adjust check script.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/check/check_python

@@ -9,5 +9,5 @@ fi
 
 ${PYTHON} -c '
 import sys
-sys.exit(sys.version_info[0] < 2 or sys.version_info[1] < 2)
-' || fail "need python version >= 2.2"
+sys.exit(sys.version_info[0] < 2 or sys.version_info[1] < 3)
+' || fail "need python version >= 2.3"