dev-python/pytest-xdist: install package for testing

pytest doesn't load the xdist plugin unless xdist has already been
installed.

Bug: https://bugs.gentoo.org/597698
Bug: https://bugs.gentoo.org/597700
Bug: https://bugs.gentoo.org/609516
Package-Manager: Portage-2.3.3_p56, Repoman-2.3.1_p49

dev-python/pytest-xdist/pytest-xdist-1.15.0.ebuild

@@ -37,6 +37,6 @@ PATCHES=(
 )
 
 python_test() {
-	find -name __pycache__ -exec rm -r '{}' + || die
+	distutils_install_for_testing
 	py.test -vv || die "Tests failed under ${EPYTHON}"
 }