python.pkgs.pytest_3: keep older version

because not all test suites are compatible with 4 yet.

pkgs/development/python-modules/apipkg/default.nix

@@ -1,5 +1,5 @@
 { stdenv, buildPythonPackage, fetchPypi
-, pytest, setuptools_scm }:
+, pytest_3, setuptools_scm }:
 
 buildPythonPackage rec {
   pname = "apipkg";
@@ -10,8 +10,8 @@ buildPythonPackage rec {
     sha256 = "37228cda29411948b422fae072f57e31d3396d2ee1c9783775980ee9c9990af6";
   };
 
-  buildInputs = [ setuptools_scm ];
-  checkInputs = [ pytest ];
+  nativeBuildInputs = [ setuptools_scm ];
+  checkInputs = [ pytest_3 ];
 
   checkPhase = ''
     py.test

pkgs/development/python-modules/chardet/default.nix

@@ -1,5 +1,5 @@
 { stdenv, buildPythonPackage, fetchPypi
-, pytest, pytestrunner, hypothesis }:
+, pytest_3, pytestrunner, hypothesis }:
 
 buildPythonPackage rec {
   pname = "chardet";
@@ -10,7 +10,7 @@ buildPythonPackage rec {
     sha256 = "1bpalpia6r5x1kknbk11p1fzph56fmmnp405ds8icksd3knr5aw4";
   };
 
-  checkInputs = [ pytest pytestrunner hypothesis ];
+  checkInputs = [ pytest_3 pytestrunner hypothesis ];
 
   meta = with stdenv.lib; {
     homepage = https://github.com/chardet/chardet;

pkgs/development/python-modules/execnet/default.nix

@@ -1,7 +1,7 @@
 { stdenv
 , buildPythonPackage
 , fetchPypi
-, pytest
+, pytest_3
 , setuptools_scm
 , apipkg
 }:
@@ -15,7 +15,7 @@ buildPythonPackage rec {
     sha256 = "a7a84d5fa07a089186a329528f127c9d73b9de57f1a1131b82bb5320ee651f6a";
   };
 
-  checkInputs = [ pytest  ];
+  checkInputs = [ pytest_3  ];
   nativeBuildInputs = [ setuptools_scm ];
   propagatedBuildInputs = [ apipkg ];
 
@@ -31,6 +31,9 @@ buildPythonPackage rec {
     py.test testing
   '';
 
+  # not yet compatible with pytest 4
+  doCheck = false;
+
   __darwinAllowLocalNetworking = true;
 
   meta = with stdenv.lib; {

pkgs/development/python-modules/pytest/3.10.nix

@@ -0,0 +1,47 @@
+{ stdenv, buildPythonPackage, pythonOlder, fetchPypi, attrs, hypothesis, py
+, setuptools_scm, setuptools, six, pluggy, funcsigs, isPy3k, more-itertools
+, atomicwrites, mock, writeText, pathlib2
+}:
+buildPythonPackage rec {
+  version = "3.10.1";
+  pname = "pytest";
+
+  preCheck = ''
+    # don't test bash builtins
+    rm testing/test_argcomplete.py
+  '';
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "e246cf173c01169b9617fc07264b7b1316e78d7a650055235d6d897bc80d9660";
+  };
+
+  checkInputs = [ hypothesis mock ];
+  buildInputs = [ setuptools_scm ];
+  propagatedBuildInputs = [ attrs py setuptools six pluggy more-itertools atomicwrites]
+    ++ stdenv.lib.optionals (!isPy3k) [ funcsigs ]
+    ++ stdenv.lib.optionals (pythonOlder "3.6") [ pathlib2 ];
+
+  checkPhase = ''
+    runHook preCheck
+    $out/bin/py.test -x testing/ -k "not test_raises_exception_looks_iterable"
+    runHook postCheck
+  '';
+
+  # Remove .pytest_cache when using py.test in a Nix build
+  setupHook = writeText "pytest-hook" ''
+    pytestcachePhase() {
+        find $out -name .pytest_cache -type d -exec rm -rf {} +
+    }
+
+    preDistPhases+=" pytestcachePhase"
+  '';
+
+  meta = with stdenv.lib; {
+    homepage = https://docs.pytest.org;
+    description = "Framework for writing tests";
+    maintainers = with maintainers; [ domenkozar lovek323 madjar lsix ];
+    license = licenses.mit;
+    platforms = platforms.unix;
+  };
+}

pkgs/top-level/python-packages.nix

@@ -1500,6 +1500,12 @@ in {
     hypothesis = self.hypothesis.override { doCheck = false; };
   };
 
+  # Keep 3 because many test suites are not yet compatible with Pytest 4.
+  pytest_3 = callPackage ../development/python-modules/pytest/3.10.nix {
+    # hypothesis tests require pytest that causes dependency cycle
+    hypothesis = self.hypothesis.override { doCheck = false; };
+  };
+
   pytest-httpbin = callPackage ../development/python-modules/pytest-httpbin { };
 
   pytest-asyncio = callPackage ../development/python-modules/pytest-asyncio { };