--- configure.ac.old	2019-12-02 20:12:56.211468994 +0000

+++ configure.ac	2019-12-02 20:13:02.041332189 +0000

@@ -74,7 +74,7 @@

   [

     AC_PATH_PROG([DOXYGEN], [doxygen])

     AS_IF([test -z "$DOXYGEN"], [AC_MSG_ERROR([doxygen not found])])

-    AC_PATH_PROG([SPHINX], [sphinx-build])

+    AC_PATH_PROG([SPHINX], [sphinx-build-3])

     AS_IF([test -z "$SPHINX"], [AC_MSG_ERROR([sphinx-build not found])])

   ]

 )