As per https://docs.python.org/3.7/reference/compound_stmts.html#except
variables used in the "except" clause are erased at the end of the
block.

We had a conflict with a nested exception using the same variable as
before.

This renames the nested variable to avoid the clash

element.py: fix unbounded variable in nested python exception

See merge request !1006

Tristan Van Berkom authored Dec 13, 2018 and Tristan Van Berkom committed Dec 13, 2018

Some external plugins depend derive from BuildElement and are broken
by BuildElement enabling this batching by default.

Instead, enable it in all of the individual build element plugin
implementations.

This fixes issue #800