python-backports-abc: depend on Python 2.x

This package is a backport from Python 3.5, so it is not needed
for Python 3.5.x environment.

Fix python-tornado dependecies, so that python-backports-abc
is only selected for Python 2.x.

Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/python-backports-abc/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_PYTHON_BACKPORTS_ABC
 	bool "python-backports-abc"
+	depends on BR2_PACKAGE_PYTHON
 	help
 	  A backport of recent additions to the 'collections.abc'
 	  module.

package/python-tornado/Config.in

@@ -3,7 +3,7 @@ config BR2_PACKAGE_PYTHON_TORNADO
 	select BR2_PACKAGE_PYTHON_ZLIB if BR2_PACKAGE_PYTHON # runtime
 	select BR2_PACKAGE_PYTHON3_ZLIB if BR2_PACKAGE_PYTHON3 # runtime
 	select BR2_PACKAGE_PYTHON_SINGLEDISPATCH if BR2_PACKAGE_PYTHON # runtime
-	select BR2_PACKAGE_PYTHON_BACKPORTS_ABC	# runtime
+	select BR2_PACKAGE_PYTHON_BACKPORTS_ABC	if BR2_PACKAGE_PYTHON # runtime
 	help
 	  Tornado is a Python web framework and asynchronous networking
 	  library, originally developed at FriendFeed.