TST: make sure test_fash uses the same seed for launching processes

Author: jreback

test_fast.sh

@@ -1 +1,8 @@
+#!/bin/bash
+
+# Workaround for pytest-xdist flaky collection order
+# https://github.com/pytest-dev/pytest/issues/920
+# https://github.com/pytest-dev/pytest/issues/1075
+export PYTHONHASHSEED=$(python -c 'import random; print(random.randint(1, 4294967295))')
+
 pytest pandas --skip-slow --skip-network -m "not single" -n 4