ENT-12764 Fixed unhandled invalid checksum error when downloading packages

[victormlg]

In the ticket mentioned in this commit, cf-remote seem to never copy downloaded files to the remote host for version 3.21.4. It is actually hanging indefinitely after seeing that the checksum of the artifact doesn't match the checksum of the downloaded package. This is because under the hood, download_package calls sys.exit if the checksum doesn't match. However, using sys.exit inside of a pooled process causes undefined behavior. The pool hangs indefinitely, waiting for the thread to return.

Previous output:

(.venv) victor-moene@victomoe:~/northern.tech/cf-remote (master)$ python3 cf_remote --version 3.21.4  install --hub debz --bootstrap debz

[email protected]
OS            : Debian 12
Architecture  : x86_64
CFEngine      : 3.21.4 (Enterprise hub)
Policy server : 172.31.38.223
CFEngine ID   : SHA=71e1dfd8ea0f275eebb822a268479e4bb7100736ecc25ca37d4e3ab404d12f1c
Private IP    : 172.31.38.223 
Binaries      : dpkg, apt, curl

Package '/home/victor-moene/.cfengine/cf-remote/packages/cfengine-nova-hub_3.21.4-1.debian12_amd64.deb' already downloaded
> Nothing is happening

New output:

(.venv) victor-moene@victomoe:~/northern.tech/cf-remote (checksumerror)$ python3 cf_remote --version 3.21.4  install --hub debz --bootstrap deb

[email protected]
OS            : Debian 12
Architecture  : x86_64
CFEngine      : 3.21.4 (Enterprise hub)
Policy server : 172.31.38.223
CFEngine ID   : SHA=71e1dfd8ea0f275eebb822a268479e4bb7100736ecc25ca37d4e3ab404d12f1c
Private IP    : 172.31.38.223 
Binaries      : dpkg, apt, curl

Package '/home/victor-moene/.cfengine/cf-remote/packages/cfengine-nova-hub_3.21.4-1.debian12_amd64.deb' already downloaded
cf_remote: Downloaded file 'cfengine-nova-hub_3.21.4-1.debian12_amd64.deb' does not match expected checksum 'dcb2ad40771f1d2003fd406a6ca5a4aa473a3813b145d84fe36f9005d31f2e8c'. Please delete the file.

[larsewi]

Great find 🚀 Looks like some unrelated code fails the linting. Probably due to the use of f-strings on Python3.5. Maybe you can fix this in a separate commit?