Installation of composer fails due to missing HOME environment variable

[tohuwabohu]

Example error message

Notice: Compiled catalog for debian-8-64.home.gateway in environment production in 0.49 seconds
Info: Applying configuration version '1458462985'
Notice: /Stage[main]/Drupal::Install/Exec[install-composer]/returns: All settings correct for using Composer
Notice: /Stage[main]/Drupal::Install/Exec[install-composer]/returns: PHP Fatal error:  Uncaught exception 'RuntimeException' with message 'The HOME or COMPOSER_HOME environment variable must be set for composer to install correctly' in -:582
Notice: /Stage[main]/Drupal::Install/Exec[install-composer]/returns: Stack trace:
Notice: /Stage[main]/Drupal::Install/Exec[install-composer]/returns: #0 -(387): getHomeDir()
Notice: /Stage[main]/Drupal::Install/Exec[install-composer]/returns: #1 -(111): installComposer(false, '/usr/local/bin', 'composer', false, false, false)
Notice: /Stage[main]/Drupal::Install/Exec[install-composer]/returns: #2 -(13): process(Array)
Notice: /Stage[main]/Drupal::Install/Exec[install-composer]/returns: #3 {main}
Notice: /Stage[main]/Drupal::Install/Exec[install-composer]/returns:   thrown in - on line 582