Update Python requirement to 2.6

CentOS 5, which was the reason for the 2.4 restriction, is EOL. CentOS
6 ships 2.6.

Bump the version to 2.6 in README. Update configure.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

README

@@ -46,7 +46,7 @@ provided by your OS distributor:
         - GCC 4.8 or later
         - GNU Binutils 2.24 or later
     * Development install of zlib (e.g., zlib-dev)
-    * Development install of Python 2, v2.4 or later (e.g., python-dev)
+    * Development install of Python 2, v2.6 or later (e.g., python-dev)
     * Development install of curses (e.g., libncurses-dev)
     * Development install of openssl (e.g., openssl-dev)
     * Development install of x11 (e.g. xorg-x11-dev)
@@ -177,7 +177,7 @@ Python Runtime Libraries
 
 Various tools, such as pygrub, have the following runtime dependencies:
 
-    * Python 2, v2.4 or later.
+    * Python 2, v2.6 or later.
           URL:    http://www.python.org/
           Debian: python
 

tools/configure

@@ -7002,15 +7002,15 @@ if test x"${PYTHONPATH}" = x"no"
 then
     as_fn_error $? "Unable to find $PYTHON, please install $PYTHON" "$LINENO" 5
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for python version >= 2.3 " >&5
-$as_echo_n "checking for python version >= 2.3 ... " >&6; }
-`$PYTHON -c 'import sys; sys.exit(eval("sys.version_info < (2, 3)"))'`
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for python version >= 2.6 " >&5
+$as_echo_n "checking for python version >= 2.6 ... " >&6; }
+`$PYTHON -c 'import sys; sys.exit(eval("sys.version_info < (2, 6)"))'`
 if test "$?" != "0"
 then
     python_version=`$PYTHON -V 2>&1`
     { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
-    as_fn_error $? "$python_version is too old, minimum required version is 2.3" "$LINENO" 5
+    as_fn_error $? "$python_version is too old, minimum required version is 2.6" "$LINENO" 5
 else
     { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }

tools/configure.ac

@@ -358,7 +358,7 @@ AS_IF([echo "$PYTHON" | grep -q "^/"], [
 ],[test -z "$PYTHON"], [PYTHON="python"],
 [AC_MSG_ERROR([PYTHON specified, but is not an absolute path])])
 AX_PATH_PROG_OR_FAIL([PYTHONPATH], [$PYTHON])
-AX_CHECK_PYTHON_VERSION([2], [3])
+AX_CHECK_PYTHON_VERSION([2], [6])
 
 AS_IF([test "$cross_compiling" != yes], [
     AX_CHECK_PYTHON_DEVEL()