Fix configure-time checks for Python

This simplifies and fixes the configure-time detection of Python.

configure.ac

@@ -6,7 +6,7 @@
 AC_PREREQ([2.69])
 LT_PREREQ([2.4.6])dnl
 
-m4_pushdef([mtime_version], [1, 2, 1])dnl
+m4_pushdef([mtime_version], [1, 2, 2])dnl
 AC_INIT([mtime],
   m4_join([],
     m4_argn(1, mtime_version).m4_argn(2, mtime_version).m4_argn(3, mtime_version),
@@ -119,18 +119,7 @@ AS_VAR_IF([enable_check], [yes],
   [CHECK_CLIBS=;CHECK_CFLAGS=])
 AM_CONDITIONAL([ENABLE_CHECK], [test x"$enable_check" = xyes])
 
-AS_VAR_IF([enable_python], [yes],
-  [dnl
-dnl AM_PATH_PYTHON does not run ACTION-IF-NOT-FOUND when the PYTHON provided by the user
-dnl is too old:
-   m4_define([mtime_python_min_version], [2.7])dnl
-   mtime_python_found=no
-   AS_IF([test -n "$PYTHON"],
-     [AM_PYTHON_CHECK_VERSION([$PYTHON], [mtime_python_min_version],
-        [mtime_python_found=yes])],
-     [AM_PATH_PYTHON([mtime_python_min_version], [mtime_python_found=yes], [:])])
-   AS_VAR_IF([mtime_python_found], [no],
-     [AC_MSG_FAILURE([cannot find suitable Python interpreter])])])
+AS_VAR_IF([enable_python], [yes], [AM_PATH_PYTHON([2.7])])
 AM_CONDITIONAL([ENABLE_PYTHON], [test x"$enable_python" = xyes])
 
 AM_MISSING_PROG([RAGEL], [ragel])