org.freedesktop.Telepathy.Connection.Interface.ContactCapabilities/caps is wrong. org.freedesktop.Telepathy.Connection.Interface.ContactCapabilities/capabilities would be right.
++ I'll file a bug on telepathy-glib to add contact attributes as generated constants, like I did for property names (unfortunately this has missed the 0.10 boat).
Merged; will be in 0.9.4. Thanks for the review!
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