dev-python/werkzeug: Force /tmp as tmpdir to fix AF_UNIX name limit

Force using /tmp for tests rather than ${T}, as the latter can easily
cause AF_UNIX socket paths to exceed the limit.

Closes: https://bugs.gentoo.org/790416
Signed-off-by: Michał Górny <mgorny@gentoo.org>

dev-python/werkzeug/werkzeug-2.0.0.ebuild

@@ -36,5 +36,7 @@ DEPEND="
 distutils_enable_tests pytest
 
 python_test() {
+	# the default portage tempdir is too long for AF_UNIX sockets
+	local -x TMPDIR=/tmp
 	epytest -p no:httpbin tests
 }