kurento-test: geckodriver (Firefox) cannot fetch console logs

geckodriver (Selenium driver for Firefox) does NOT implement fetching
console logs through its API (like Chrome does):
driver.manage().logs() throws org.openqa.selenium.json.JsonException.

For more information, follow this issue:
mozilla/geckodriver#284

This commit:

-> Adds comments and explanations about this, and catch the
org.openqa.selenium.json.JsonException that is thrown when the test is
running Firefox and log fetching is attempted.

-> Enables Firefox profile settings that should output all console logs
to stdout.

kurento-integration-tests/kurento-test/src/main/java/org/kurento/test/base/BrowserTest.java

@@ -173,9 +173,20 @@ public void teardownBrowserTest() {
           WebDriver webDriver = browser.getWebDriver();
           if (webDriver != null) {
             String screenshotFileName = getDefaultOutputFile("-" + browserId + ".png");
-            getOrCreatePage(browserId).takeScreeshot(screenshotFileName);
-            browserLogs.put(browserId,
-                webDriver.manage().logs().get(LogType.BROWSER));
+            try {
+              getOrCreatePage(browserId).takeScreeshot(screenshotFileName);
+            } catch (IOException e) {
+              log.warn("Error taking screenshot from browser '{}': {}", browserId, e.getMessage());
+            }
+            try {
+              browserLogs.put(browserId, webDriver.manage().logs().get(LogType.BROWSER));
+            } catch (org.openqa.selenium.json.JsonException e) {
+              // TODO: Remove this catch() if/when Firefox geckodriver implements the logs() method
+              // (https://github.com/mozilla/geckodriver/issues/284)
+              log.warn(
+                  "Error fetching console logs from browser '{}': {} -- This is expected on Firefox, geckodriver doesn't implement 'driver.manage().logs()'. More info: https://github.com/mozilla/geckodriver/issues/284",
+                  browserId, e.getMessage());
+            }
           } else {
             log.warn("It was not possible to recover logs for '{}' "
                 + "since browser is no longer available (maybe "

kurento-integration-tests/kurento-test/src/main/java/org/kurento/test/browser/Browser.java

@@ -395,6 +395,15 @@ private void createFirefoxBrowser(DesiredCapabilities capabilities) throws Malfo
     firefoxOptions.addPreference("media.autoplay.default", 0);
     firefoxOptions.addPreference("media.autoplay.enabled.user-gestures-needed", false);
 
+    // Route all console logs to stdout (https://github.com/mozilla/geckodriver/issues/284#issuecomment-458305621)
+    //
+    // This is needed because geckodriver (Selenium driver for Firefox) does NOT
+    // implement fetching console logs through its API (like Chrome does):
+    // driver.manage().logs() throws org.openqa.selenium.json.JsonException.
+    // For more information, follow this issue: https://github.com/mozilla/geckodriver/issues/284
+    firefoxOptions.addPreference("devtools.console.stdout.chrome", true); // Enable the stdout logging in console API when used in UI ("chrome") contexts
+    firefoxOptions.addPreference("devtools.console.stdout.content", true); // Enable the stdout logging in console API when used in content contexts
+
     // This allows to load pages with self-signed certificates
     capabilities.setCapability("acceptInsecureCerts", true);