Add test environment using pluggy from master branch

Fix #2737

.travis.yml

@@ -18,10 +18,12 @@ env:
     - TOXENV=py27-xdist
     - TOXENV=py27-trial
     - TOXENV=py27-numpy
+    - TOXENV=py27-pluggymaster
     - TOXENV=py35-pexpect
     - TOXENV=py35-xdist
     - TOXENV=py35-trial
     - TOXENV=py35-numpy
+    - TOXENV=py35-pluggymaster
     - TOXENV=py27-nobyte
     - TOXENV=doctesting
     - TOXENV=freeze

appveyor.yml

@@ -21,10 +21,12 @@ environment:
   - TOXENV: "py27-xdist"
   - TOXENV: "py27-trial"
   - TOXENV: "py27-numpy"
+  - TOXENV: "py27-pluggymaster"
   - TOXENV: "py35-pexpect"
   - TOXENV: "py35-xdist"
   - TOXENV: "py35-trial"
   - TOXENV: "py35-numpy"
+  - TOXENV: "py35-pluggymaster"
   - TOXENV: "py27-nobyte"
   - TOXENV: "doctesting"
   - TOXENV: "freeze"

setup.py

@@ -43,7 +43,11 @@ def has_environment_marker_support():
 
 
 def main():
-    install_requires = ['py>=1.4.33', 'six>=1.10.0','setuptools', 'pluggy>=0.4.0,<0.5']
+    install_requires = ['py>=1.4.33', 'six>=1.10.0', 'setuptools']
+    # if _PYTEST_SETUP_SKIP_PLUGGY_DEP is set, skip installing pluggy;
+    # used by tox.ini to test with pluggy master
+    if '_PYTEST_SETUP_SKIP_PLUGGY_DEP' not in os.environ:
+        install_requires.append('pluggy>=0.4.0,<0.5')
     extras_require = {}
     if has_environment_marker_support():
         extras_require[':python_version=="2.6"'] = ['argparse', 'ordereddict']

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 minversion = 2.0
 distshare = {homedir}/.tox/distshare
-# make sure to update environment list on appveyor.yml
+# make sure to update environment list in travis.yml and appveyor.yml
 envlist =
     linting
     py26
@@ -12,7 +12,7 @@ envlist =
     py36
     py37
     pypy
-    {py27,py35}-{pexpect,xdist,trial,numpy}
+    {py27,py35}-{pexpect,xdist,trial,numpy,pluggymaster}
     py27-nobyte
     doctesting
     freeze
@@ -21,11 +21,14 @@ envlist =
 [testenv]
 commands = pytest --lsof -rfsxX {posargs:testing}
 passenv = USER USERNAME
+setenv=
+    pluggymaster: _PYTEST_SETUP_SKIP_PLUGGY_DEP=1
 deps =
     hypothesis>=3.5.2
     nose
     mock
     requests
+    pluggymaster: git+https://github.com/pytest-dev/pluggy.git@master
 
 [testenv:py26]
 commands = pytest --lsof -rfsxX {posargs:testing}