Motivation for this change

Failing hydra build for 19.03. Figured I'd update to the package in the process.
Python3: https://hydra.nixos.org/build/90113585
Python2: https://hydra.nixos.org/build/90308802

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

Tests

• nix-build -A pytest-rerunfailures
• (Looks to be the only expression to use this package) nix-build -A tmuxp

{ pkgs ? import <nixpkgs> {} }:

pkgs.stdenv.mkDerivation rec {
  name = "xonsh";
  buildInputs = with pkgs; [
    tmuxp
    python3Packages.pytest
    python3Packages.pytest-rerunfailures
  ];
}

import pytest
import time

def test_foo():
    assert int(time.time()) % 10 in (1)

nix-shell --pure -I nixpkgs=/path/to/nixpkgs 
pytest --reruns 10 --reruns-delay 1
tmuxp --version  # I don't know how to use tmuxp
tmuxp --help

Additional Notes

https://pypi.org/project/pytest-rerunfailures/#id1