Pin pytest-timeout to fix the build.

Author: anntzer

.travis.yml

@@ -55,9 +55,12 @@ env:
     - NUMPY=numpy
     - PANDAS=
     - PYPARSING=pyparsing
-    - PYTEST='pytest>=3.4'
+    # pytest-timeout master depends on pytest>=3.6.  Testing with pytest 3.4 is
+    # still supported; this is tested by the first matrix entry.
+    - PYTEST='pytest>=3.6'
     - PYTEST_COV=pytest-cov
     - PYTEST_PEP8=
+    - PYTEST_TIMEOUT=pytest-timeout
     - SPHINX=sphinx
     # Variables controlling the build.
     - MPLLOCALFREETYPE=1
@@ -86,6 +89,7 @@ matrix:
         - PYPARSING=pyparsing==2.0.1
         - PYTEST=pytest==3.4
         - PYTEST_COV=pytest-cov==2.3.1
+        - PYTEST_TIMEOUT=pytest-timeout==1.2.1  # Newer pytest-timeouts don't support pytest 3.4.
         - SPHINX=sphinx==1.3
     - python: 3.5
       env:
@@ -177,7 +181,7 @@ install:
         pytest-faulthandler \
         $PYTEST_PEP8 \
         pytest-rerunfailures \
-        pytest-timeout \
+        $PYTEST_TIMEOUT \
         pytest-xdist
   - |
     # Install matplotlib