--- /dev/null
+#!/bin/bash
+
+# Not entirely sure why these executables don't seem to be available in the
+# $PATH when running from tox. Calling out to `which` seems to fix it, at the
+# expense of making the script a bit obtuse
+
+mktemp=$(which mktemp)
+cat=$(which cat)
+grep=$(which grep)
+PYTHON_EXECUTABLE=`which python`
+STDERR_FILE=$($mktemp)
+INVALID="→"
+
+echo "stderr file created: $STDERR_FILE"
+
+INVALID="$INVALID" $PYTHON_EXECUTABLE $1 2> ${STDERR_FILE}
+
+retVal=$?
+
+if [ $retVal -ne 0 ]; then
+ echo "Failed test: Unexpected failure from running Python script"
+ echo "Below is output of stderr captured:"
+ $cat "${STDERR_FILE}"
+ exit $retVal
+fi
+
+$grep --quiet "$INVALID" ${STDERR_FILE}
+
+retVal=$?
+if [ $retVal -ne 0 ]; then
+ echo "Failed test: expected to find \"${INVALID}\" character in tmpfile: \"${STDERR_FILE}\""
+ echo "Below is output of stderr captured:"
+ $cat "${STDERR_FILE}"
+fi
+exit $retVal