Remove python2-ism in root package (#14223)

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

@@ -6,7 +6,6 @@
 
 from spack import *
 import sys
-import types
 
 
 class Root(CMakePackage):
@@ -450,7 +449,7 @@ def _process_opts(self, *opt_lists):
 
         def _process_opt(opt_name, cond_or_variant=None):
             val = cond_or_variant if \
-                isinstance(cond_or_variant, types.BooleanType) else \
+                isinstance(cond_or_variant, bool) else \
                 ('+{variant}'.format(variant=cond_or_variant or opt_name)
                  in self.spec)
             return '-D{opt}:BOOL={val}'.format(opt=opt_name, val='ON' if