dev-python/pytest-shutil: Block py2 pytest-virtualenv

Since dev-python/pytest normally loads all plugins, and PMs don't
necessarily enforce dependencies of these that are not part of @world,
it is possible to break their depgraph and break pytest on py2.7
completely.  Add a blocker to make that harder.

Signed-off-by: Michał Górny <mgorny@gentoo.org>

dev-python/pytest-shutil/pytest-shutil-1.7.0-r1.ebuild

@@ -27,6 +27,10 @@ RDEPEND="
 	dev-python/mock[${PYTHON_USEDEP}]
 	dev-python/termcolor[${PYTHON_USEDEP}]
 "
+# block pytest plugins that will be broken by the upgrade
+RDEPEND+="
+	!<dev-python/pytest-virtualenv-1.7.0-r1[python_targets_python2_7(-)]
+"
 
 BDEPEND="
 	${RDEPEND}