Bug#1087864: docopt.cpp: autopkgtest regression due to new CMake deprecation warning

[roehling at debian.org]

Source: docopt.cpp
Version: 0.6.3-4
Severity: serious
User: cmake at packages.debian.org
Usertags: cmake-3.31

Dear maintainer,

your package has an autopkgtest regression with CMake 3.31. CMake has
deprecated backwards compatibility for versions earlier than 3.10,
which causes cmake_minimum_required() and/or cmake_policy() to emit a
warning on stderr, thereby causing your autopkgtest to fail. The
tests should be unaffected otherwise.

To avoid this warning from cmake_minimum_required() you have two
options:

1. Bump the minimum required version to at least 3.10. For reference,
the CMake version in oldstable is 3.18 and in oldoldstable is 3.13.

2. Add a maximum version with the ... operator. For example, instead
of cmake_minimum_required(VERSION 3.7) use
cmake_minimum_required(VERSION 3.7...3.31).

In either case, please verify that the requested policy profile is
compatible with your package. This is very likely the case you have a
non-trivial autopkgtest which passes after the change.