do-release-upgrade doesn't work with C locale

[yvs]

How to repeat:

% LANG=C do-release-upgrade ~
Traceback (most recent call last):
  File "/usr/bin/do-release-upgrade", line 121, in <module>
    print(_("Checking for a new Ubuntu release"))
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-12: ordinal not in range(128)

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: ubuntu-release-upgrader-core 1:18.10.10
ProcVersionSignature: Ubuntu 4.15.0-34.37-generic 4.15.18
Uname: Linux 4.15.0-34-generic x86_64
ApportVersion: 2.20.10-0ubuntu11
Architecture: amd64
CrashDB: ubuntu
Date: Tue Oct 9 12:14:04 2018
InstallationDate: Installed on 2014-01-10 (1732 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to cosmic on 2018-10-08 (0 days ago)

[Juhani Numminen (jsonic)]

Isn't that a known problem with Python?

A workaround might be to use the C.UTF-8 locale instead of C.

From https://www.python.org/dev/peps/pep-0538/
> The simplest way to deal with this problem for currently released versions of CPython is to explicitly set a more sensible locale when launching the application. For example:
>
> LC_CTYPE=C.UTF-8 python3 ...