remove tar and gzip dependencies

E: python-installsystems: depends-on-essential-package-without-using-version depends: gzip
E: python-installsystems: depends-on-essential-package-without-using-version depends: tar
N:
N:    The package declares a depends on an essential package, e.g. dpkg,
N:    without using a versioned depends. Packages do not need to depend on
N:    essential packages; essential means that they will always be present.
N:    The only reason to list an explicit dependency on an essential package
N:    is if you need a particular version of that package, in which case the
N:    version should be given in the dependency.
N:
N:    Refer to Debian Policy Manual section 3.5 (Dependencies) for details.
N:
N:    Severity: important, Certainty: certain
N: