work around PermissionErrors in /tmp dirs by test_run_fail() test

Author: ibressler

tox.ini

@@ -36,3 +36,6 @@ nb_diff_replace =
     /cells/*/outputs/*/text plugins\:\s.*\n "plugin info ...\n"
     /cells/*/outputs/*/text "exec_cwd\=\\\'\/([A-z0-9-_+]+\/)*[A-z0-9-_+]+\\\'" "exec_cwd=/.../<dir>"
     /cells/*/outputs/*/traceback \<ipython\-input\-[\-0-9a-zA-Z]*\> "<ipython-input-XXXX>"
+
+# work around PermissionErrors in /tmp dirs by test_run_fail() test
+addopts = --basetemp=tmp