Decreased the flakiness of upload_tar function

common/test/acceptance/pages/studio/import_export.py

@@ -178,7 +178,15 @@ class ImportMixin(object):
         asset_file_path = self.file_path(tarball_filename)
         # Make the upload elements visible to the WebDriver.
         self.browser.execute_script('$(".file-name-block").show();$(".file-input").show()')
+        # Upload the file.
         self.q(css='input[type="file"]')[0].send_keys(asset_file_path)
+        # Upload the same file again. Reason behind this is to decrease the
+        # probability or fraction of times the failure occur. Please be
+        # noted this doesn't eradicate the root cause of the error, it
+        # just decreases to failure rate to minimal.
+        # Jira ticket reference: TNL-4191.
+        self.q(css='input[type="file"]')[0].send_keys(asset_file_path)
+        # Some of the tests need these lines to pass so don't remove them.
         self._wait_for_button()
         click_css(self, '.submit-button', require_notification=False)
 

common/test/acceptance/tests/studio/test_import_export.py

@@ -182,7 +182,6 @@ class ImportTestMixin(object):
         """
         return []
 
-    @flaky      # TODO, fix this: TNL-4191
     def test_upload(self):
         """
         Scenario: I want to upload a course or library for import.