This error is throwing when building tp-mc in the buildbot slaves:

libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I../../src -I.. -pthread -I/var/lib/buildbot/install/usr/include/telepathy-1.0 -I/usr/include/dbus-1.0 -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/lib/dbus-1.0/include -pthread -I/usr/include/dbus-1.0 -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/lib/dbus-1.0/include -pthread -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -DG_LOG_DOMAIN=\"mcd\" -DMCD_PLUGIN_LOADER_DIR=\"/var/lib/buildbot/install/usr/lib/mission-control-plugins.0\" -DMC_DISABLE_DEPRECATED -I../.. -Wall -Wextra -Wdeclaration-after-statement -Wshadow -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wsign-compare -Wnested-externs -Wpointer-arith -Wformat-security -Winit-self -Wno-missing-field-initializers -Wno-unused-parameter -Werror -Wno-error=missing-field-initializers -Wno-error=unused-parameter -g -O2 -DENABLE_DEBUG -MT mcd-manager.lo -MD -MP -MF .deps/mcd-manager.Tpo -c ../../src/mcd-manager.c  -fPIC -DPIC -o .libs/mcd-manager.o
../../src/mcd-manager.c: In function ‘mcd_manager_setup’:
../../src/mcd-manager.c:201:5: error: ‘tp_connection_manager_call_when_ready’ is deprecated (declared at /var/lib/buildbot/install/usr/include/telepathy-1.0/telepathy-glib/connection-manager.h:130): Use tp_proxy_prepare_async instead [-Werror=deprecated-declarations]
cc1: all warnings being treated as errors
make[3]: *** [mcd-manager.lo] Error 1
make[3]: Leaving directory `/var/lib/buildbot/telepathy/telepathy-mission-control-i386/build/build/src'
make[2]: *** [all] Error 2
rm _gen/Account_Interface_Compat.xml _gen/Account_Interface_Addressing.xml _gen/dispatcher.xml _gen/Account_Interface_External_Password_Storage.xml _gen/Connection_Manager_Interface_Account_Storage.xml _gen/Account_Manager_Interface_Query.xml _gen/Account_Interface_Conditions.xml _gen/Account_Interface_Hidden.xml _gen/Account_Manager_Interface_Hidden.xml
make[2]: Leaving directory `/var/lib/buildbot/telepathy/telepathy-mission-control-i386/build/build/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/var/lib/buildbot/telepathy/telepathy-mission-control-i386/build/build'
make: *** [all] Error 2
program finished with exit code 2

See here for more details: http://buildbot.telepathy.im:8010/builders/telepathy-mission-control%20-%20i386/builds/93/steps/compile/logs/stdio