Bug 1545207 - Mock the Search Service region test in Telemetry Client Tests r=raphael

We don't want spurious net connections, so we should mock the result.
In addition, we need to mock it to a specific non-North-American region to
ensure we don't cause an extra change to browser.search.region which may split
the subsession in the middle of our tests.

Differential Revision: https://phabricator.services.mozilla.com/D28059

--HG--
extra : moz-landing-system : lando

toolkit/components/telemetry/tests/marionette/harness/telemetry_harness/runner.py

@@ -25,6 +25,10 @@ class TelemetryTestRunner(BaseMarionetteTestRunner):
         # Set Firefox Client Telemetry specific preferences
         prefs.update(
             {
+                # Fake the geoip lookup to always return Germany to:
+                #   * avoid net access in tests
+                #   * stabilize browser.search.region to avoid an extra subsession (bug 1545207)
+                "browser.search.geoip.url": "data:application/json,{\"country_code\": \"DE\"}",
                 "toolkit.telemetry.server": "{}/pings".format(SERVER_URL),
                 "toolkit.telemetry.initDelay": 1,
                 "toolkit.telemetry.minSubsessionLength": 0,