No additional dependencies except Python 2.7/3.x interpreter are required.

Preferable way is to download tarball with the signature from official
website:

    $ wget http://pygost.cypherpunks.ru/pygost-3.7.tar.xz
    $ wget http://pygost.cypherpunks.ru/pygost-3.7.tar.xz.sig
    $ gpg --verify pygost-3.7.tar.xz.sig pygost-3.7.tar.xz
    $ xz -d < pygost-3.7.tar.xz | tar xf -
    $ cd pygost-3.7
    $ python setup.py install

But also you can use PIP (NO authentication is performed!):

    $ pip install pygost==3.7

You have to verify downloaded tarballs integrity and authenticity to be
sure that you retrieved trusted and untampered software. GNU Privacy
Guard is used for that purpose.

For the very first time it is necessary to get signing public key and
import it. It is provided below, but you should check alternative
resources.

    pub   rsa2048/0xE6FD1269CD0C009E 2016-09-13
          F55A 7619 3A0C 323A A031  0E6B E6FD 1269 CD0C 009E
    uid   PyGOST releases <pygost at cypherpunks dot ru>

    Look in PUBKEY.asc file.
    $ gpg --auto-key-locate dane --locate-keys pygost at cypherpunks dot ru
    $ gpg --auto-key-locate wkd --locate-keys pygost at cypherpunks dot ru