petsc: configure works with python3 in current petsc@develop - and will work...

petsc: configure works with python3  in current petsc@develop - and will work in future releases [3.11+] (#10380)

var/spack/repos/builtin/packages/petsc/package.py

@@ -106,7 +106,8 @@ class Petsc(Package):
     depends_on('mpi', when='+mpi')
 
     # Build dependencies
-    depends_on('python@2.6:2.8', type='build')
+    depends_on('python@2.6:2.8', type='build', when='@:3.10.99')
+    depends_on('python@2.6:2.8,3.4:', type='build', when='@3.11:')
 
     # Other dependencies
     depends_on('metis@5:~int64+real64', when='@:3.7.99+metis~int64+double')