Composer 2.0.10 breaks Travis builds for core 8.9 and 9.0

Problem/Motivation

Starting on 23 Feb 2021 the Travis test builds for Core 8.9 and Core 9.0 failed with error

"PHP Fatal error:  Class Composer\Package\AliasPackage contains 3 abstract methods and must therefore be declared abstract or implement the remaining methods (Composer\Package\PackageInterface::getArchiveName, Composer\Package\PackageInterface::isDefaultBranch, Composer\Package\PackageInterface::setSourceDistReferences)"

See https://travis-ci.com/github/jonathan1055/scheduler/builds/218004960

Core 9.2 runs OK. Core 8.8 is already rolling back to Composer 1 so is not affected. All versions of core ran OK up to Feb 22.

The log shows 'Composer version 2.0.10 2021-02-23 16:11:37' which implies that this new version, released this day, causes the problem. The builds yesterday all ran fine with 'Composer version 2.0.9 2021-01-27 16:09:27'

Proposed resolution

For core versions 8.9 and 9.0 use composer self-update 2.0.9 to get back to the non-broken version.