Ubunutu14.10:Installation fails with Debootstrap Error :Invalid Release signature (key id 40976EAF437D05B5)

[bugproxy]

Problem Description
======================
I was installing ubuntu 14.10 then after disk partitioning option installation failed with below error

      ?????????????????? [!!] Install the base system ???????????????????
      ? ?
  ????? Debootstrap Error ? ???
  ? ? The following error occurred: ? ?
  ? ? ? ?
  ? ? Invalid Release signature (key id 40976EAF437D05B5) ? ?
  ? Ch? ? ?
  ? ? Check /var/log/syslog or see virtual console 4 for the details. ? ?
  ????? ? ???
      ? <Go Back> <Continue> ?
      ? ?
      ???????????????????????????????????????????????????????????????????

    ?????????????????? [!!] Install the base system ???????????????????
      ? ?
      ? Failed to install the base system ?
      ? The base system installation into /target/ failed. ?
      ? ?
      ? Check /var/log/syslog or see virtual console 4 for the details. ?
      ? ?
      ? <Go Back> <Continue> ?
      ? ?
      ???????????????????????????????????????????????????????????????????

     ??????????????????? [!!] Install the base system ????????????????????
     ? ?
     ? Installation step failed ?
     ? An installation step failed. You can try to run the failing item ?
     ? again from the menu, or skip it and choose something else. The ?
     ? failing step is: Install the base system ?
     ? ?
     ? <Continue> ?
     ? ?
     ?????????????????????????????????????????????????????????????????????

I have attached /var/log/syslog file with this bug .It allowed to proceed with installation so taking back the system and attaching the logs for debugging .

[bugproxy (bugproxy)]

Default Comment by Bridge

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1381457/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2014-10-16 07:58 EDT-------
Same issue with kernel not found in daily Oct 16th - see Launchpad ID # 1381732

SO until this Ubuntu bug is fixed, nothing can be done on current one.

[Mathieu Trudel-Lapierre (cyphermox)]

Could this be a failure from debootstrap to properly retrieve the necessary files?

The key itself should be correct: it seems to be used just fine earlier to validate packages.

Is there are proxy involved in the retrieval of files in this case? It's the only thing I can think of right now to explain this failure.

Thanks!

[Launchpad Janitor (janitor)]

[Expired for debian-installer (Ubuntu) because there has been no activity for 60 days.]