Invoke test runner once per file for pypy shard.

.travis.yml

@@ -77,4 +77,4 @@ install:
   - pip install -U tox "setuptools<34"
 
 script:
-  - tox -v
+  - ./scripts/ci.sh

scripts/ci.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -euo pipefail
+
+if [[ "$TOXENV" == "pypy" ]]; then
+  echo "pypy shard detected. invoking workaround for https://github.com/travis-ci/travis-ci/issues/9706"
+  for test_file in $(/bin/ls -1 tests/test_*.py | grep -v test_integration.py); do
+    echo "testing ${test_file}"
+    tox -v "${test_file}"
+  done
+else
+  tox -v
+fi