Add compatibility for Python 3.8+ (#71)

Author: kevlened

.travis.yml

@@ -21,5 +21,8 @@ jobs:
     - name: py37
       python: "3.7"
       env: TOXENV=py37-coverage
+    - name: py38
+      python: "3.8"
+      env: TOXENV=py38-coverage
     - name: lint
       script: pipenv run lint

README.md

@@ -53,6 +53,14 @@ pytest --tests-per-worker auto
 pytest --workers 2 --tests-per-worker auto
 ```
 
+## Notice
+
+Beginning with Python 3.8, forking behavior is forced on macOS at the expense of safety.
+
+    Changed in version 3.8: On macOS, the spawn start method is now the default. The fork start method should be considered unsafe as it can lead to crashes of the subprocess. See bpo-33725.
+
+[Source](https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods)
+
 ## License
 
 MIT

pytest_parallel/__init__.py

@@ -1,30 +1,33 @@
 import os
 import py
+import sys
 import time
 import math
 import pytest
 import _pytest
 import platform
 import threading
+import multiprocessing
 from tblib import pickling_support
 from multiprocessing import Manager, Process
 
+# In Python 3.8 and later, the default on macOS is spawn.
+# We force forking behavior at the expense of safety.
+#
+# "On macOS, the spawn start method is now the default. The fork start method should be
+#  considered unsafe as it can lead to crashes of the subprocess. See bpo-33725."
+#
+# https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods
+if sys.platform.startswith('darwin'):
+    multiprocessing.set_start_method('fork')
+
 __version__ = '0.0.10'
 
 
 def parse_config(config, name):
     return getattr(config.option, name, config.getini(name))
 
 
-def force(fn):
-    while True:
-        try:
-            return fn()
-        except ConnectionRefusedError:
-            time.sleep(.1)
-            continue
-
-
 def pytest_addoption(parser):
     workers_help = ('Set the max num of workers (aka processes) to start '
                     '(int or "auto" - one per core)')
@@ -179,7 +182,7 @@ class ParallelRunner(object):
     def __init__(self, config):
         self._config = config
         self._manager = Manager()
-        self._log = py.log.Producer("pytest-parallel")
+        self._log = py.log.Producer('pytest-parallel')
 
         reporter = config.pluginmanager.getplugin('terminalreporter')
 

tox.ini

@@ -3,6 +3,7 @@ envlist =
   flake8
   py36
   py37
+  py38
 
 [testenv]
 deps =