From c1e003ff2f8a43189d48b7194ec8556aa3d88641 Mon Sep 17 00:00:00 2001
From: Frederik Rietdijk <fridh@fridh.nl>
Date: Sun, 4 Nov 2018 09:45:41 +0100
Subject: [PATCH] Python: reduce amount of warnings when building with
 `buildPython*`

By default all warnings were printed. This occasionally resulted in
a lot of warnings leading to builds being killed.

This commit reduces the amount of warnings printed.
---
 pkgs/development/interpreters/python/mk-python-derivation.nix | 4 ++++
 pkgs/development/python-modules/pytest/default.nix            | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/interpreters/python/mk-python-derivation.nix b/pkgs/development/interpreters/python/mk-python-derivation.nix
index 63ffdbb8c0a..ef8ee4e5425 100644
--- a/pkgs/development/interpreters/python/mk-python-derivation.nix
+++ b/pkgs/development/interpreters/python/mk-python-derivation.nix
@@ -101,6 +101,10 @@ toPythonModule (python.stdenv.mkDerivation (builtins.removeAttrs attrs [
     ${python.interpreter} ${./catch_conflicts}/catch_conflicts.py
   '' + attrs.postFixup or '''';
 
+  # Print fewer warnings so we have less noise in our logs
+  # The amount of warnings also caused builds to be terminated.
+  PYTHONWARNINGS="once";
+
   meta = {
     # default to python's platforms
     platforms = python.meta.platforms;
diff --git a/pkgs/development/python-modules/pytest/default.nix b/pkgs/development/python-modules/pytest/default.nix
index 9412a750a9a..ad8c8d9ad0d 100644
--- a/pkgs/development/python-modules/pytest/default.nix
+++ b/pkgs/development/python-modules/pytest/default.nix
@@ -24,7 +24,8 @@ buildPythonPackage rec {
 
   checkPhase = ''
     runHook preCheck
-    $out/bin/py.test -x testing/
+    # Re-enable warnings because the test suite relies on it.
+    PYTHONWARNINGS= $out/bin/py.test -x testing/
     runHook postCheck
   '';