Bug#1054712: ensmallen: FTBFS: adam_test.cpp:17:10: fatal error: catch2/catch.hpp: No such file or directory

[Drew Parsons]

Source: ensmallen
Followup-For: Bug #1054712
Control: forwarded 1054712 https://github.com/mlpack/ensmallen/issues/372

This error occurs because of the upgrade of catch2 from v2 to v3.

Unfortunately ensmallen upstream don't sound very enthusiastic about
dealing with it, https://github.com/mlpack/ensmallen/issues/372

Arguably the catch developers made life unjustifiablydifficult. Maybe
they should have released catch3 rather than catch2 v3.

On the other hand, judging by the patch for termpaint, the required
changes are likely to be essentially trivial, e.g. 
  #include "catch2/catch_all.hpp"
instead of 
  #include "catch2/catch.hpp"

cf.
https://github.com/termpaint/termpaint/commit/dc293554b745b3f010445e9445e620399f8ee2f7