Need a more meaningful 502 error page for process start failure

[pan-wang]

In case ANCM cannot start backend process for whatever reason(e.g., wrong processPath value), a 502 error page was returned to client without any debugging/actionable hint. We may need to improve this error page for ANCM only to help debugging experience.

[Tratcher]

Reminder: Set the charset. Right now Chrome guesses the wrong encoding and the page renders full of replacement characters.

[Tratcher]

<�!DOCTYPE html> <�html><�head><�title> IIS 502.5 Error <�/title> <�style type="text/css"><�/style><�/head><�body> <�div id = "content"> <�div class = "content-container"><�h3> HTTP Error 502.5 - Process Failure <�/h3><�/div> <�div class = "content-container"> <�fieldset> <�h4> Most likely causes : <�/h4> <�ul><�li> Failed to start the backend process.<�/li> <�li> The process got started but crashed.<�/li> <�li> The process failed to listen on given port.<�/li><�/ul><�/fieldset> <�/div> <�div class = "content-container"> <�fieldset><�h4>Things you can try : <�/h4> <�ul><�li>Look at windows event log for details.<�/li> <�li>Use DebugDiag to troubleshoot the Asp.Net Core application.<�/li><�/ul><�/fieldset> <�/div> <�/div><�/body><�/html>

[muratg]

I believe this is done.