Bug#888995: FTBFS: async_execution_load_test needs /run/user

Source: dbus-cpp
Version: 5.0.0+18.04.20171031-1
Severity: important
Tags: upstream
Justification: fails to build from source
User: [email protected]
Usertags: mips mipsel

Builds of dbus-cpp for several architectures (armhf, mips, mipsel, and
the non-release architectures alpha and x32) failed with errors along
the lines of

  15/15 Test  #1: async_execution_load_test ........***Failed  300.02 sec
  Running main() from gmock_main.cc
  [==========] Running 1 test from 1 test case.
  [----------] Global test environment set-up.
  [----------] 1 test from AsyncExecutionLoadTest
  [ RUN      ] AsyncExecutionLoadTest.RepeatedlyInvokingAnAsyncFunctionWorks
  dbus[25970]: Unable to set up transient service directory: XDG_RUNTIME_DIR "/run/user/114" not available: No such file or directory
  /<<BUILDDIR>>/dbus-cpp-5.0.0+18.04.20171031/tests/async_execution_load_test.cpp:134: Failure
  Value of: ec->wait_for(std::chrono::minutes{5})
    Actual: false (Current count of 378 does not match 500)
  Expected: true
  dbus[25966]: Attempted to unregister path (path[0] = org path[1] = freedesktop) which isn't registered
  [  FAILED  ] AsyncExecutionLoadTest.RepeatedlyInvokingAnAsyncFunctionWorks (300015 ms)
  [----------] 1 test from AsyncExecutionLoadTest (300015 ms total)
  
  [----------] Global test environment tear-down
  [==========] 1 test from 1 test case ran. (300015 ms total)
  [  PASSED  ] 0 tests.
  [  FAILED  ] 1 test, listed below:
  [  FAILED  ] AsyncExecutionLoadTest.RepeatedlyInvokingAnAsyncFunctionWorks
  
   1 FAILED TEST
  
  
  93% tests passed, 1 tests failed out of 15
  
  Total Test time (real) = 300.02 sec
  
  The following tests FAILED:
  	  1 - async_execution_load_test (Failed)
  Errors while running CTest

Presumably, these architectures' autobuilders happen to lack /run/user.
(I'm just tagging the two affected mips architectures for now, as
presumably representative here.)

Could you please take a look?