Permission denied dconf WARNING although the tests passed

I write automation tests with Selenium WebDriver and TestNG on FF v59.0. My OS is Ubuntu.

When I execute test within IntelliJ IDE, the test is successful and I don't get warning.

When I execute test via Terminal with mvn test, the test is also successful, but I get these warning as shown in log below:

-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running TestSuite

Firefox test starting ...
1521729328615   geckodriver     INFO    geckodriver 0.20.0
1521729328618   geckodriver     INFO    Listening on 127.0.0.1:11492
1521729328754   mozrunner::runner       INFO    Running command: "/usr/lib/firefox/firefox" "-marionette" "-profile" "/tmp/rust_mozprofile.7orKMUEcEqE4"

1521729329110   Marionette      INFO    Enabled via --marionette
1521729330182   Marionette      INFO    Listening on port 46037
1521729330258   Marionette      WARN    TLS certificate errors will be ignored for this session

Mar 22, 2018 3:35:30 PM org.openqa.selenium.remote.ProtocolHandshake createSession
INFO: Detected dialect: W3C

(/usr/lib/firefox/firefox:5528): dconf-WARNING **: Unable to open /var/lib/snapd/desktop/dconf/profile/user: Permission denied

Pausing for 5 seconds:  1 2 3 4 5
.........................
Page Loaded.

*** UTM:SVC TimerManager:registerTimer called after profile-before-change notification. Ignoring timer registration for id: telemetry_modules_ping
1521729345488   geckodriver::marionette ERROR   Failed to stop browser process
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 17.482 sec

Results :

Tests run: 1, Failures: 0, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 19.647 s

So I get a warning:

(/usr/lib/firefox/firefox:5528): dconf-WARNING **: Unable to open /var/lib/snapd/desktop/dconf/profile/user: Permission denied

and an error:

1521729345488 geckodriver::marionette ERROR Failed to stop browser process

Although the test is successful and browser is closed after test. How to fix these warning and error? Or should I ignore them because the test is passed anyway.