In my company, we must access Web sites on the Internet via authentication proxy server which adopts BASIC authentication.
When calling "git clone" via HTTPS from GitHub, we experience no problem and proxy authentication works normally, however, in case if we click on "Check For Updates", we encounter below error messages saying proxy authentication is required. As a result, we are unable to update our Source Tree.

ERROR [2019-04-10 11:21:20,371] [1] [Sourcetree.Installer.Squirrel.Utils.UpdateHelper] [Log] - Couldn't read staging user ID
ERROR [2019-04-10 11:21:20,376] [1] [Sourcetree.Installer.Squirrel.Utils.UpdateHelper] [Log] - Couldn't read staging user ID
ERROR [2019-04-10 11:21:24,662] [1] [Sourcetree.Installer.Squirrel.Utils.UpdateHelper] [Log] - Unable to check for Updates.
System.Net.WebException: The remote server returned an error: (407) Proxy authentication required
at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)
at System.Net.WebClient.DownloadBitsResponseCallback(IAsyncResult result)
— End of stack trace from previous location where exception was thrown —
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Squirrel.Utility.<LogIfThrows>d__43`1.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Squirrel.FileDownloader.<DownloadUrl>d__3.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Squirrel.UpdateManager.CheckForUpdateImpl.<CheckForUpdate>d__2.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Squirrel.UpdateManager.<CheckForUpdate>d__7.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Sourcetree.Installer.Squirrel.Utils.UpdateHelper.<CheckForUpdate>d__16.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Sourcetree.Installer.Squirrel.Utils.UpdateHelper.<HasAvailableUpdates>d__17.MoveNext()