This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.
The lxml module relies on native libraries. When linting, pylint will
not load native libraries for security reasons. Thus, it can't find some
symbols exported by lxml, causing linting to fail. Whitelisting lxml
prevents this.
