failure if target provided in config and directory already exists.

[Scott Moser]

Subiquity provides /target as in config like:
  install: {target: /target}

if /target already exists, then WorkingDir will fail and stack trace.

stack trace looks something like this:

Running command ['tar', '-cvf', '/var/log/curtin/curtin-error-logs.tar', 'curtin-logs-2018-06-07-13-33'] with allowed return codes [0] (capture=True)
Wrote: /var/log/curtin/curtin-error-logs.tar
finish: cmd-install: FAIL: curtin command install
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/curtin/commands/install.py", line 469,
in cmd_install
    raise e
  File "/usr/lib/python3/dist-packages/curtin/commands/install.py", line 433,
in cmd_install
    workingd = WorkingDir(cfg)
  File "/usr/lib/python3/dist-packages/curtin/commands/install.py", line 119,
in __init__
    os.mkdir(p)
FileExistsError: [Errno 17] File exists: '/target'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/curtin/commands/main.py", line 201, in
main
    ret = args.func(args)
  File "/usr/lib/python3/dist-packages/curtin/commands/install.py", line 473,
in cmd_install
    copy_install_log(logfile, workingd.target, log_target_path)
UnboundLocalError: local variable 'workingd' referenced before assignment
local variable 'workingd' referenced before assignment

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: curtin 18.1-17-gae48e86f-0ubuntu1~18.04.1
ProcVersionSignature: User Name 4.15.0-22.24-generic 4.15.17
Uname: Linux 4.15.0-22-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.9-0ubuntu7.1
Architecture: amd64
Date: Thu Jun 7 13:45:03 2018
Ec2AMI: ami-0000059f
Ec2AMIManifest: FIXME
Ec2AvailabilityZone: nova
Ec2InstanceType: m1.small
Ec2Kernel: unavailable
Ec2Ramdisk: unavailable
PackageArchitecture: all
ProcEnviron:
 TERM=screen-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: curtin
UpgradeStatus: No upgrade log present (probably fresh install)

[Scott Moser (smoser)]

An upstream commit landed for this bug.

To view that commit see the following URL:
https://git.launchpad.net/curtin/commit/?id=9d0e557e

[Launchpad Janitor (janitor)]

This bug was fixed in the package curtin - 18.1-25-g9d0e557e-0ubuntu1

---------------
curtin (18.1-25-g9d0e557e-0ubuntu1) cosmic; urgency=medium

  * New upstream snapshot.
    - Fix WorkingDir class to support already existing target directory.
      (LP: #1775622)
    - Fix extraction of local filesystem image. (LP: #1775630)
    - Fix tip-pyflakes imported but unused call to util.get_platform_arch
    - subp: update return value of subp with combine_capture=True.
    - tox: add a xenial environments, default envlist changes.
    - tests: Fix race on utcnow during timestamped curtin-log dir creation
      (LP: #1772481)
    - curtainer: patch source version from --source.
    - pyflakes: fix unused variable references identified by pyflakes 2.0.0.

 -- Scott Moser <email address hidden> Thu, 07 Jun 2018 14:59:20 -0400

[Ryan Harper (raharper)]

This bug is believed to be fixed in curtin in version 18.2. If this is still a problem for you, please make a comment and set the state back to New

Thank you.