Hmm, psutil worked on OS/X but not so on linux, so don't install it on travis.

.travis.yml

@@ -18,7 +18,7 @@ install:
     # Then start installing our deps so they can be cached. Note that use of --build-options / --global-options / --install-options
     # disables the cache.
     # We need wheel>=0.26 on Python 3.5. See previous revisions.
-    - travis_retry pip install -U wheel psutil
+    - travis_retry pip install -U wheel
     - travis_retry pip install -U tox cython greenlet pep8 pyflakes "coverage>=4.0" "coveralls>=1.0"
 script:
     - if [[ $TRAVIS_PYTHON_VERSION == '2.7' && $LINT == true ]]; then python setup.py develop && make travis_test_linters; elif [[ $LINT == false && $TRAVIS_PYTHON_VERSION == 'pypy' ]]; then python setup.py develop && make fulltoxtest; elif [[ $LINT == false ]]; then python setup.py develop && make fulltoxtest; fi

greentest/test__makefile_ref.py

@@ -55,6 +55,7 @@ else:
     # (Running 14 tests takes 3.964s with lsof and 0.046 with psutil)
     # However, it still doesn't completely solve the issue on Windows: fds are reported
     # as -1 there, so we can't fully check those.
+    # XXX: Note: installing psutil on the travis linux vm caused failures.
     process = psutil.Process()
 
     def get_open_files():
@@ -461,7 +462,7 @@ class TestSSL(Test):
             self.assertEqual(f.read(), 'test_serverssl_makefile2')
             self.assertEqual(f.read(), '')
             f.close()
-            if WIN and psutil and not PY3:
+            if WIN and psutil:
                 # Hmm?
                 self.extra_allowed_open_states = (psutil.CONN_CLOSE_WAIT,)
             self.assert_open(client_socket, fileno)