Use numpy 1.17.3 for python 3.8

travis/build-wheels.sh

@@ -35,6 +35,8 @@ for PYBIN in /opt/python/*/bin; do
         NUMPY_VERSION="1.14.5"
     elif [[ "${PYBIN}" == *cp35* ]]; then
         NUMPY_VERSION="1.9.3"
+    elif [[ "${PYBIN}" == *cp38* ]]; then
+        NUMPY_VERSION="1.17.3"
     else
         NUMPY_VERSION="1.8.2"
     fi