Comment 2 for bug 1336833

I did test of apache2 (2.4.18-2ubuntu3.5) on Xenial.

I can enable configuration file with white spaces with following command.

# a2ensite "this\ is\ a\ test.conf"
Enabling site this is a test.
To activate the new configuration, you need to run:
  service apache2 reload

a2ensite supports only *.conf files for reasons of compatibility with main configuration.

# grep sites-enabled /etc/apache2/apache2.conf
# `-- sites-enabled
# * Configuration files in the mods-enabled/, conf-enabled/ and sites-enabled/
IncludeOptional sites-enabled/*.conf