meson: check for python2 mako

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
diff --git a/meson.build b/meson.build
index 02f43ee..329495e 100644
--- a/meson.build
+++ b/meson.build
@@ -53,6 +53,10 @@
 endif
 
 prog_python2 = find_program('python2')
+has_mako = run_command(prog_python2, '-c', 'import mako')
+if has_mako.returncode() != 0
+  error('Python (2.x) mako module required to build mesa.')
+endif
 
 cc = meson.get_compiler('c')
 if cc.get_id() == 'gcc' and cc.version().version_compare('< 4.4.6')