+# XXX JEH this method seems entirely useless.
+# $self->invoke_impl('foo', @_);
+# $self->foo(@_);
+# The second is easier to both read and write.
+#
+# Turns out that one build system overrides this method,
+# perl_build uses it to set an env vatiable before each method
+# call. But that's unnecessary; it could just set it in its constructor.
+#
+# And there's another version of this method in the derifed class below,
+# which just adds another parameter to the method call. That is used only
+# by the python_distutils build system, to add a --build-base parameter
+# to two calls to python. It could be manually added to those two calls
+# with less fuss.