package/python-keyring: depend comment on BR2_PACKAGE_PYTHON3

The user shouldn't view the comment on the python2 menu.

Signed-off-by: Asaf Kahlon <asafka7@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 6a932714d31440203b707394e1927f05c49f40e1)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/python-keyring/Config.in

@@ -11,4 +11,5 @@ config BR2_PACKAGE_PYTHON_KEYRING
 	  https://pypi.python.org/pypi/keyring
 
 comment "python-keyring needs a toolchain w/ C++"
+	depends on BR2_PACKAGE_PYTHON3
 	depends on !BR2_INSTALL_LIBSTDCPP