pkgsrc build looking for PYPACKAGE suggestion?

While building Samba4, I have a build failure because 'make' is looking 
for Python 2.7 based packages, but Python 3.8 packages are what are 
available.

A message is printed stating that the system default is "38", but that 
the build will use "27", by setting PYPACKAGE.  It then says if this is 
not right, interrupt and set PYPACKAGE as needed.

The problem is that it has nothing to say about where/how to make the 
change.

Pointers on how to do this would be much appreciated.

Bob