Alternative to @jmp answer, I can recommend to use instead of Appium's app the FakeTraveler It has not the disadvantage to run a lot of adb permission commands, which not really work out of the box and without search google why setting permission ACCESS_MOCK_LOCATION don't work.
FakeTraveler guides you automatic to right developer setting ♥
I had the same problem and found a solution, fixing the issues that sphakka had in his answer.
Create these 2 files:
With the following content: