Add requirements.txt and fix PySNMP dependency versioning

[dlenski]

PySNMP 4.x is now thoroughly obsolete. It cannot be used at all with Python 3.12, which removed from the standard library the asyncore module on which it depended.

Additionally, pysnmp 6.2 removed the "oneliner" interface which this script currently uses.

Therefore, in order to continue using this script:

• with Python 3.12: PySNMP >= 6 and < 6.2 is required
• with older Python 3.x: PySNMP >= 4 and < 6.2 is required

[dlenski]

Both #46 and #47 appear to result from users installing incompatible versions of PySNMP, and should be fixed by this.

[peterhoeg]

Another way to deal with this and make things work with recent 6.2+ versions of pysnmp is to bring in pysnmplib which has the old functions as well as a recent pysnmp. Works great here.

[dlenski]

Another way to deal with this and make things work with recent 6.2+ versions of pysnmp is to bring in pysnmplib which has the old functions as well as a recent pysnmp. Works great here.

It appears that pysnmplib (https://pypi.org/project/pysnmplib, https://github.com/pysnmp/pysnmp) has the same issue as pysnmp (https://pypi.org/project/pysnmp, https://github.com/lextudio/pysnmp)… the combination of recent-library-version and Python 3.12 doesn't work due to the asyncore requirement.

If I'm mistaken, can you show exactly how you're installing and using pysnmplib with oh-brother and Python 3.12, @peterhoeg?

[peterhoeg]

Sure, so this on nixos (but works anywhere nix does) with the following:

{
  lib,
  fetchFromGitHub,
  python3Packages,
}:

let
  pypkgs = python3Packages;

in
pypkgs.buildPythonApplication rec {
  pname = "oh-brother";
  version = "0-unstable-2025-06-01";

  pyproject = false;

  src = fetchFromGitHub {
    owner = "CauldronDevelopmentLLC";
    repo = "oh-brother";
    rev = "d7cd5b06beb12e60d178791d84fa0512861a2694";
    hash = "sha256-nD7OO6yrjTFpIdzm/cQHctRk/IKZbyDAkrfnzY1VIVw=";
  };

  postPatch = ''
    sed -i '16i import importlib.util' oh-brother.py
    sed -i '17i import importlib.machinery' oh-brother.py
  '';

  dependencies = with pypkgs; [
    pyasyncore
    pysnmplib # *MUST* come before pysnmp as it shares the pysnmp python namespace
    # https://github.com/CauldronDevelopmentLLC/oh-brother/blob/d7cd5b06beb12e60d178791d84fa0512861a2694/requirements.txt
    pysnmp
    pysnmp-pyasn1
  ];

  installPhase = ''
    runHook preInstall

    install -Dm555 oh-brother.py $out/bin/${meta.mainProgram}
    install -Dm444 -t $out/share/doc/${pname} *.md

    runHook postInstall
  '';

  # no tests
  doCheck = true;

  meta = with lib; {
    description = "Update Brother Printer Firmware";
    license = licenses.gpl2Only;
    mainProgram = "oh-brother";
  };
}

And here are the full closure details which shows all the versions:

Details

/nix/store/1jj2lq1kzys105rqq5n1a2r4v59arz43-mailcap-2.1.54
/nix/store/6hqzbvz50bm87hcj4qfn51gh7arxj8a6-gcc-14.2.1.20250322-libgcc
/nix/store/yypqcvqhnv8y4zpicgxdigp3giq81gzb-libunistring-1.3
/nix/store/6nkqdqzpa75514lhglgnjs5k4dklw4sb-libidn2-2.3.8
/nix/store/za53jjhjl1xajv3y1zpjvr9mh4w0c1ay-xgcc-14.2.1.20250322-libgcc
/nix/store/cg9s562sa33k78m63njfn1rw47dp9z0i-glibc-2.40-66
/nix/store/7c0v0kbrrdc2cqgisi78jdqxn73n3401-gcc-14.2.1.20250322-lib
/nix/store/8pviily4fgsl02ijm65binz236717wfs-openssl-3.4.1
/nix/store/90c412b9wqhfny300rg5s2gpsbrqb31q-libffi-3.4.8
/nix/store/vfmnmqsnfiiqmphy7ffh2zqynsxfck1q-ncurses-6.5
/nix/store/971mpk4nqhqcxggx0yi60w9y1ya570bj-readline-8.2p13
/nix/store/j0bzxly2rvcym1zkhn393adiqcwn8np6-expat-2.7.1
/nix/store/pa60s415p92gnhv5ffz1bmfgzzfvhvd8-xz-5.8.1
/nix/store/qizipyz9y17nr4w4gmxvwd3x4k0bp2rh-libxcrypt-4.4.38
/nix/store/qkzkz12l4q06lzbji0ifgynzrd44bpjs-gdbm-1.25-lib
/nix/store/qyihkwbhd70ynz380whj3bsxk1d2lyc4-tzdata-2025b
/nix/store/srby6wmvg7dp454pwb6qvaxdiri38sc1-zlib-1.3.1
/nix/store/yfjzkkkyxcalyj7l1n4d4y6s81i65hmy-sqlite-3.48.0
/nix/store/r03ly1w54924k8fag1dhjl3yrllj6czd-util-linux-minimal-2.41-lib
/nix/store/wyf93cvh25b2xg82mkjcpmwgcspk0ggr-mpdecimal-4.0.0
/nix/store/xy4jjgw87sbgwylm5kn047d9gkbhsr9x-bash-5.2p37
/nix/store/zrnqzhcvlpiycqbswl0w172y4bpn0lb4-bzip2-1.0.8
/nix/store/8w718rm43x7z73xhw9d6vh8s4snrq67h-python3-3.12.10
/nix/store/azbbrwb8glahagaqqsaa4akv20903lm3-python3.12-charset-normalizer-3.4.1
/nix/store/lf8ilk72n59c1yg7zbwvqd5mimlqzpqk-python3.12-urllib3-2.3.0
/nix/store/n0v27hx3n5sc51z833jbmkgi4sm086qg-python3.12-idna-3.10
/nix/store/6fv8ayzjvgyl3rdhxp924zdhwvhz2iq6-nss-cacert-3.111
/nix/store/y85rrr4sx62x27fka04sncbbd7g8g59j-python3.12-certifi-2025.01.31
/nix/store/0lln9m37mw7cjdf02krfpiwd4clwdlwl-python3.12-requests-2.32.3
/nix/store/kyxcsmk6m1j5czlsyq038xpnpfa55j6r-python3.12-pycryptodomex-3.21.0
/nix/store/zrqxiwpi62smy5pvdpl4w5kax50gc3ii-python3.12-ply-3.11
/nix/store/w148pnnhbif3maplqx34izwdr8w255f1-python3.12-pysnmp-pysmi-1.1.12
/nix/store/wk9pdhgxvyn2xp110qnqz03vvch07n1i-python3.12-pysnmp-pyasn1-1.1.3
/nix/store/0rs75zbmrkh8mhlfhwpj4i3l72v7g9ry-python3.12-pysnmplib-5.0.24
/nix/store/2w6vn2qlffkc386lfkb2324kk4vvw53f-python3.12-pyasyncore-1.0.4
/nix/store/8rgbflgzd942wdq9p2iijzy0g32dazhb-python3.12-pyasn1-0.6.1
/nix/store/x7nyn4jv80amafdya2xgm1a07m0hinap-python3.12-markupsafe-3.0.2
/nix/store/kn0svpfjpbx8zl1rp0f0rzh2ray0c2xs-python3.12-jinja2-3.1.6
/nix/store/mhscxvpf98amzkih54jyhqpw7xx6i5lc-python3.12-pycparser-2.22
/nix/store/w56z2iwqp4c3k0bx1rnh2kkmh8jysk48-python3.12-cffi-1.17.1
/nix/store/vg7494b4p4if8a126w3ickkphc559idb-python3.12-cryptography-44.0.2
/nix/store/qs0p3bnryd8z7ipmq271lqg49w79g36l-python3.12-pysnmpcrypto-0.1.0
/nix/store/sqzwcwn5gfs7kh5z2ljx4l30z1ikw7iw-python3.12-pysmi-1.5.9
/nix/store/qfjjlmhmqfd0dawpgm8lx3na0w9mx8ff-python3.12-pysnmp-7.1.16
/nix/store/k5592hf58ljd6935361d325yfs86lkhs-oh-brother-0-unstable-2025-06-01

[dlenski]

  dependencies = with pypkgs; [
    pyasyncore
    pysnmplib # *MUST* come before pysnmp as it shares the pysnmp python namespace
    # https://github.com/CauldronDevelopmentLLC/oh-brother/blob/d7cd5b06beb12e60d178791d84fa0512861a2694/requirements.txt
    pysnmp
    pysnmp-pyasn1
  ];

Ahhh. You've got pyasyncore as well: "This package contains the asyncore module as found in Python versions prior to 3.12. It is provided so that existing code relying on import asyncore is able to continue being used without significant refactoring."