The "newlatex2e" writer used to be in the Docutils core until version 0.7. It is, however orphaned for a long time, deprecated since version 0.6, and now moved to this sandbox directory.
Please report documents that worked with "newlatex2e" but fail with "latex2e" to the docutils mail list or the bug tracker.
To get back a working "newlatex" writer, copy/move/link the directory newlatex2e to docutils/writers/ in the standard Docutils package and rst2newlatex.py to a place in the binary PATH.
The test input file standalone_rst_newlatex.txt works if placed in docutils/test/functional/input.