Problems building current stable/2.20 - new python.h requirements (?)

[pkx166h]

Hello,

If I checkout current stable/2.20 and then try to build LilyPond I fail 
during the 'configure' check with this

--snip--

...

config.status: creating config.make
config.status: creating config.hh

ERROR: Please install required programs:  Python.h (python-devel, 
python-dev or libpython-dev package)
--snip--

Yet if I checkout current master, staging etc. I don't get this.

Is this expected - i.e. I know 'stable/2.20' is probably a bit of a 
misnomer, but I was surprised to find something that was required over 
and above what current master needed. Or is this something related to 
all the GUB stuff that has been going on and this will need to be 
'ported' into 2.21 (master)?

I only mention this after trying to test a patch for changes.tely for 
2.20's eventual release 
(https://sourceforge.net/p/testlilyissues/issues/5601/ ) and failing 
with this requirement.

Obviously I can install this stuff but wanted to check on this (for me 
anyway) unexpected configure error.

Thanks.

James