Output of the automated test for this bug:

Loading config defaults from "./tox.ini"
Using defaults:
          color True
  show_snippets True
   show_skipped False
        dry_run False
    show_source True
   show_timings True
 stdout_capture False
 stderr_capture False
    log_capture False
 logging_format %(asctime)s:%(levelname)s:%(name)s:%(message)s
  logging_level info
  steps_catalog False
        summary True
          junit True
          stage None
       userdata {}
 default_format pretty
   default_tags 
scenario_outline_annotation_schema {name} -- @{row.id} {examples.name}
more_formatters {}
Using default path "./features"
Trying base directory: /home/renan/work/ubuntu-advantage-client/features
--- job suffix: None
Config options:
  image_clean = True
  destroy_instances = True
  ephemeral_instance = False
  snapshot_strategy = False
  cloud_credentials_path = None
  contract_token = <REDACTED>
  contract_token_staging = <REDACTED>
  contract_token_staging_expired = <REDACTED>
  machine_type = lxd.container
  private_key_file = None
  private_key_name = uaclient-integration
  reuse_image = None
  debs_path = None
  artifact_dir = None
  install_from = InstallationSource.PROPOSED
  custom_ppa = None
  custom_ppa_keyid = None
  userdata_file = None
  check_version = 27.11.2~16.04.1
  sbuild_chroot = None
@uses.config.contract_token
Feature: Enable command behaviour when attached to an Ubuntu Pro subscription # features/attached_enable.feature:2

  @series.lts @uses.config.contract_token @uses.config.machine_type.lxd.container
  Scenario Outline: APT auth file is edited correctly on enable -- @1.1 ubuntu release                               # features/attached_enable.feature:1135
    Given a `xenial` machine with ubuntu-advantage-tools installed                                                   # features/steps/steps.py:61
    When I attach `contract_token` with sudo                                                                         # features/steps/steps.py:510
    When I run `wc -l /etc/apt/auth.conf.d/90ubuntu-advantage` with sudo                                             # features/steps/steps.py:373
    Then I will see the following on stdout                                                                          # features/steps/steps.py:611
      """
      2 /etc/apt/auth.conf.d/90ubuntu-advantage
      """
    When I run `cp /etc/apt/auth.conf.d/90ubuntu-advantage /etc/apt/auth.conf.d/90ubuntu-advantage.backup` with sudo # features/steps/steps.py:373
    When I run `pro disable esm-infra` with sudo                                                                     # features/steps/steps.py:373
    When I run `cp /etc/apt/auth.conf.d/90ubuntu-advantage.backup /etc/apt/auth.conf.d/90ubuntu-advantage` with sudo # features/steps/steps.py:373
    When I run `pro enable esm-infra` with sudo                                                                      # features/steps/steps.py:373
    When I run `wc -l /etc/apt/auth.conf.d/90ubuntu-advantage` with sudo                                             # features/steps/steps.py:373
    Then I will see the following on stdout                                                                          # features/steps/steps.py:611
      """
      2 /etc/apt/auth.conf.d/90ubuntu-advantage
      """
    When I run `pro enable cis` with sudo                                                                            # features/steps/steps.py:373
    When I run `wc -l /etc/apt/auth.conf.d/90ubuntu-advantage` with sudo                                             # features/steps/steps.py:373
    Then I will see the following on stdout                                                                          # features/steps/steps.py:611
      """
      3 /etc/apt/auth.conf.d/90ubuntu-advantage
      """

1 feature passed, 0 failed, 30 skipped
1 scenario passed, 0 failed, 474 skipped
13 steps passed, 0 failed, 8510 skipped, 0 undefined
Took 1m46.529s
___________________________________ summary ____________________________________
  behave-lxd-16.04: commands succeeded
  congratulations :)