Comment 1 for bug 1306936

The error from your pastebin was:
014-04-11 20:30:21,047 ERROR not handled exception:
Traceback (most recent call last):

  File "/tmp/ubuntu-release-upgrader-9bqw0n/trusty", line 10, in <module>
    sys.exit(main())

  File "/tmp/ubuntu-release-upgrader-9bqw0n/DistUpgrade/DistUpgradeMain.py", line 243, in main
    if app.run():

  File "/tmp/ubuntu-release-upgrader-9bqw0n/DistUpgrade/DistUpgradeController.py", line 1826, in run
    return self.fullUpgrade()

  File "/tmp/ubuntu-release-upgrader-9bqw0n/DistUpgrade/DistUpgradeController.py", line 1717, in fullUpgrade
    if not self.updateSourcesList():

  File "/tmp/ubuntu-release-upgrader-9bqw0n/DistUpgrade/DistUpgradeController.py", line 807, in updateSourcesList
    self.sources.save()

  File "/tmp/ubuntu-release-upgrader-9bqw0n/DistUpgrade/sourceslist.py", line 416, in save
    files[source.file].write(source.str())

UnicodeEncodeError: 'ascii' codec can't encode character u'\xfc' in position 156: ordinal not in range(128)

(please include error messages directly in Launchpad reports instead of linking to pastebins that may or may not keep this information around for the lifetime of the bug.)

Can you attach your /etc/apt/sources.list? I haven't seen this failure, but it's in line with other problems we've had before regarding encoding handling in do-release-upgrader and friends. also, could you show the output of 'locale' on your console?