Adjustments for ubuntu focal and python 3.8

[rodrigogansobarbieri]

• Add dependency dh-python for properly building package
• Address "RuntimeError: dictionary keys changed during iteration" when creating instance in OpenStack.

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[rodrigogansobarbieri]

@neiljerram all I know is that if the dependency is not present, then we hit this error when building: https://paste.ubuntu.com/p/R7nJ6tYn8B/

By just adding the dependency, the error does not happen and the package builds successfully

[nelljerram]

Thanks @rodrigogansobarbieri , I'll just record the error message here, in case someone has ideas about it in future.

• docker run --rm --user 0:0 -v /home/ubuntu/packaging2/packaging:/code -w /code/networking-calico calico-build/focal dpkg-buildpackage -I -S dpkg-buildpackage: info: source package networking-calico dpkg-buildpackage: info: source version 1:3.18.0~0.dev-focal dpkg-buildpackage: info: source distribution focal dpkg-buildpackage: info: source changed by Neil Jerram neil@tigera.io dpkg-source -I --before-build . dpkg-source: info: using options from networking-calico/debian/source/options: --tar-ignore=.tox/ --tar-ignore=env/* debian/rules clean dh clean --with python3,systemd --buildsystem=pybuild dh: error: unable to load addon python3: Can't locate Debian/Debhelper/Sequence/python3.pm in @INC (you may need to install the Debian::Debhelper::Sequence::python3 module) (@INC contains: /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.30.0 /usr/local/share/perl/5.30.0 /usr/lib/x86_64-linux-gnu/perl5/5.30 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.30 /usr/share/perl/5.30 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base) at (eval 11) line 1. BEGIN failed--compilation aborted at (eval 11) line 1.