Everything works like expected
augtool> print /files/etc/sudoers/
/files/etc/sudoers
/files/etc/sudoers/#comment[1] = "sudoers file."
/files/etc/sudoers/Defaults[1]
/files/etc/sudoers/Defaults[1]/always_set_home
/files/etc/sudoers/Defaults[2]
/files/etc/sudoers/Defaults[2]/env_reset
/files/etc/sudoers/#comment[2] = "Defaults:testuser !syslog, !log_output"
/files/etc/sudoers/Defaults[3]
/files/etc/sudoers/Defaults[3]/env_keep
/files/etc/sudoers/Defaults[3]/env_keep/var[1] = "LANG"
/files/etc/sudoers/Defaults[3]/env_keep/var[2] = "LC_ADDRESS"
/files/etc/sudoers/Defaults[3]/env_keep/var[3] = "LC_CTYPE"
/files/etc/sudoers/Defaults[3]/env_keep/var[4] = "LC_COLLATE"
/files/etc/sudoers/Defaults[3]/env_keep/var[5] = "LC_IDENTIFICATION"
/files/etc/sudoers/Defaults[3]/env_keep/var[6] = "LC_MEASUREMENT"
/files/etc/sudoers/Defaults[3]/env_keep/var[7] = "LC_MESSAGES"
/files/etc/sudoers/Defaults[3]/env_keep/var[8] = "LC_MONETARY"
/files/etc/sudoers/Defaults[3]/env_keep/var[9] = "LC_NAME"
/files/etc/sudoers/Defaults[3]/env_keep/var[10] = "LC_NUMERIC"
/files/etc/sudoers/Defaults[3]/env_keep/var[11] = "LC_PAPER"
/files/etc/sudoers/Defaults[3]/env_keep/var[12] = "LC_TELEPHONE"
/files/etc/sudoers/Defaults[3]/env_keep/var[13] = "LC_TIME"
/files/etc/sudoers/Defaults[3]/env_keep/var[14] = "LC_ALL"
/files/etc/sudoers/Defaults[3]/env_keep/var[15] = "LANGUAGE"
/files/etc/sudoers/Defaults[3]/env_keep/var[16] = "LINGUAS"
/files/etc/sudoers/Defaults[3]/env_keep/var[17] = "XDG_SESSION_COOKIE"
/files/etc/sudoers/Defaults[4]
/files/etc/sudoers/Defaults[4]/targetpw
/files/etc/sudoers/Defaults[4]/#comment = "ask for the password of the target user i.e. root"
/files/etc/sudoers/spec[1]
/files/etc/sudoers/spec[1]/user = "ALL"
/files/etc/sudoers/spec[1]/host_group
/files/etc/sudoers/spec[1]/host_group/host = "ALL"
/files/etc/sudoers/spec[1]/host_group/command = "ALL"
/files/etc/sudoers/spec[1]/host_group/command/runas_user = "ALL"
/files/etc/sudoers/spec[1]/#comment = "WARNING! Only use this together with 'Defaults targetpw'!"
/files/etc/sudoers/spec[2]
/files/etc/sudoers/spec[2]/user = "root"
/files/etc/sudoers/spec[2]/host_group
/files/etc/sudoers/spec[2]/host_group/host = "ALL"
/files/etc/sudoers/spec[2]/host_group/command = "ALL"
/files/etc/sudoers/spec[2]/host_group/command/runas_user = "ALL"
/files/etc/sudoers/spec[3]
/files/etc/sudoers/spec[3]/user = "vagrant"
/files/etc/sudoers/spec[3]/host_group
/files/etc/sudoers/spec[3]/host_group/host = "ALL"
/files/etc/sudoers/spec[3]/host_group/command = "ALL"
/files/etc/sudoers/spec[3]/host_group/command/runas_user = "ALL"
/files/etc/sudoers/spec[3]/host_group/command/tag = "NOPASSWD"
augtool> set /files/etc/sudoers/
augtool> set /files/etc/sudoers/spec[3]/user vagrant1
augtool> save
Saved 1 file(s)

when i make the comment[2] to a real setting i can not save the file anymore

augtool> print /files/etc/sudoers/
/files/etc/sudoers
/files/etc/sudoers/#comment = "sudoers file."
/files/etc/sudoers/Defaults[1]
/files/etc/sudoers/Defaults[1]/always_set_home
/files/etc/sudoers/Defaults[2]
/files/etc/sudoers/Defaults[2]/env_reset
/files/etc/sudoers/Defaults[3]
/files/etc/sudoers/Defaults[3]/type = ":testuser"
/files/etc/sudoers/Defaults[3]/syslog
/files/etc/sudoers/Defaults[3]/syslog/negate
/files/etc/sudoers/Defaults[3]/log_output
/files/etc/sudoers/Defaults[3]/log_output/negate
/files/etc/sudoers/Defaults[4]
/files/etc/sudoers/Defaults[4]/env_keep
/files/etc/sudoers/Defaults[4]/env_keep/var[1] = "LANG"
/files/etc/sudoers/Defaults[4]/env_keep/var[2] = "LC_ADDRESS"
/files/etc/sudoers/Defaults[4]/env_keep/var[3] = "LC_CTYPE"
/files/etc/sudoers/Defaults[4]/env_keep/var[4] = "LC_COLLATE"
/files/etc/sudoers/Defaults[4]/env_keep/var[5] = "LC_IDENTIFICATION"
/files/etc/sudoers/Defaults[4]/env_keep/var[6] = "LC_MEASUREMENT"
/files/etc/sudoers/Defaults[4]/env_keep/var[7] = "LC_MESSAGES"
/files/etc/sudoers/Defaults[4]/env_keep/var[8] = "LC_MONETARY"
/files/etc/sudoers/Defaults[4]/env_keep/var[9] = "LC_NAME"
/files/etc/sudoers/Defaults[4]/env_keep/var[10] = "LC_NUMERIC"
/files/etc/sudoers/Defaults[4]/env_keep/var[11] = "LC_PAPER"
/files/etc/sudoers/Defaults[4]/env_keep/var[12] = "LC_TELEPHONE"
/files/etc/sudoers/Defaults[4]/env_keep/var[13] = "LC_TIME"
/files/etc/sudoers/Defaults[4]/env_keep/var[14] = "LC_ALL"
/files/etc/sudoers/Defaults[4]/env_keep/var[15] = "LANGUAGE"
/files/etc/sudoers/Defaults[4]/env_keep/var[16] = "LINGUAS"
/files/etc/sudoers/Defaults[4]/env_keep/var[17] = "XDG_SESSION_COOKIE"
/files/etc/sudoers/Defaults[5]
/files/etc/sudoers/Defaults[5]/targetpw
/files/etc/sudoers/Defaults[5]/#comment = "ask for the password of the target user i.e. root"
/files/etc/sudoers/spec[1]
/files/etc/sudoers/spec[1]/user = "ALL"
/files/etc/sudoers/spec[1]/host_group
/files/etc/sudoers/spec[1]/host_group/host = "ALL"
/files/etc/sudoers/spec[1]/host_group/command = "ALL"
/files/etc/sudoers/spec[1]/host_group/command/runas_user = "ALL"
/files/etc/sudoers/spec[1]/#comment = "WARNING! Only use this together with 'Defaults targetpw'!"
/files/etc/sudoers/spec[2]
/files/etc/sudoers/spec[2]/user = "root"
/files/etc/sudoers/spec[2]/host_group
/files/etc/sudoers/spec[2]/host_group/host = "ALL"
/files/etc/sudoers/spec[2]/host_group/command = "ALL"
/files/etc/sudoers/spec[2]/host_group/command/runas_user = "ALL"
/files/etc/sudoers/spec[3]
/files/etc/sudoers/spec[3]/user = "vagrant1"
/files/etc/sudoers/spec[3]/host_group
/files/etc/sudoers/spec[3]/host_group/host = "ALL"
/files/etc/sudoers/spec[3]/host_group/command = "ALL"
/files/etc/sudoers/spec[3]/host_group/command/runas_user = "ALL"
/files/etc/sudoers/spec[3]/host_group/command/tag = "NOPASSWD"
augtool> set /files/etc/sudoers/spec[3]/user vagrant
augtool> save
error: Failed to execute command
saving failed (run 'errors' for details)
augtool> errors
Error in /etc/sysconfig/network/if-up.d/ndp-proxy:58.27 (parse_failed)
  Syntax error
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/shellvars.aug:194.12-.60:

Error in /etc/sysconfig/network/if-up.d/SuSEfirewall2:22.3 (parse_failed)
  Syntax error
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/shellvars.aug:194.12-.60:

Error in /etc/sysconfig/network/ifroute-lo:4.3 (parse_failed)
  Syntax error
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/shellvars.aug:194.12-.60:

Error in /etc/sysconfig/network/if-down.d/ndp-proxy:58.27 (parse_failed)
  Syntax error
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/shellvars.aug:194.12-.60:

Error in /etc/default/star:32.8 (parse_failed)
  Syntax error
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/shellvars.aug:194.12-.60:

Error in /etc/apache2/conf.d/workers.properties:2.1 (parse_failed)
  Syntax error
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/httpd.aug:98.10-.44:

Error in /etc/krb5.conf:6.0 (parse_failed)
  Get did not match entire input
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/krb5.aug:154.10-156.66:

Error in /etc/sudoers (put_failed)
  Failed to match

    { /type/ = /[!:>@][^\001-\004\t\n \\]+/ }?
    ({ /always_set_home|authenticate|env_editor|env_reset|fqdn|ignore_dot|ignore_local_sudoers|insults|log_host|log_year|long_otp_prompt|mail_always|mail_badpass|mail_no_host|mail_no_perms|mail_no_user|noexec|path_info|passprompt_override|preserve_groups|requiretty|root_sudo|rootpw|runaspw|set_home|set_logname|setenv|shell_noargs|stay_setuid|targetpw|tty_tickets|visiblepw|closefrom_override|closefrom_override|compress_io|fast_glob|log_input|log_output|pwfeedback|umask_override|use_pty/ }
      | { /passwd_tries/ = /[0-9]+/ }
      | { /((loglinelen|passwd_timeout|timestamp_timeout|umask))|((loglinelen|passwd_timeout|timestamp_timeout|umask))/ = /(([0-9]+))/ }
      | { /badpass_message|editor|mailsub|noexec_file|passprompt|runas_default|syslog_badpri|syslog_goodpri|timestampdir|timestampowner|secure_path/ = /[^\001-\004\t\n "#,=\\]+|"[^\001-\004\n"#,=\\]+"/ }
      | { /((exempt_group|lecture|lecture_file|listpw|logfile|mailerflags|mailerpath|mailto|mailfrom|syslog|verifypw))|((exempt_group|lecture|lecture_file|listpw|logfile|mailerflags|mailerpath|mailto|mailfrom|syslog|verifypw))/ = /(([^\001-\004\t\n "#,=\\]+|"[^\001-\004\n"#,=\\]+"))/ }
      | { /((env_check|env_delete|env_keep))|((env_check|env_delete|env_keep))/ })
(
    { /always_set_home|authenticate|env_editor|env_reset|fqdn|ignore_dot|ignore_local_sudoers|insults|log_host|log_year|long_otp_prompt|mail_always|mail_badpass|mail_no_host|mail_no_perms|mail_no_user|noexec|path_info|passprompt_override|preserve_groups|requiretty|root_sudo|rootpw|runaspw|set_home|set_logname|setenv|shell_noargs|stay_setuid|targetpw|tty_tickets|visiblepw|closefrom_override|closefrom_override|compress_io|fast_glob|log_input|log_output|pwfeedback|umask_override|use_pty/ }
      | { /passwd_tries/ = /[0-9]+/ }
      | { /((loglinelen|passwd_timeout|timestamp_timeout|umask))|((loglinelen|passwd_timeout|timestamp_timeout|umask))/ = /(([0-9]+))/ }
      | { /badpass_message|editor|mailsub|noexec_file|passprompt|runas_default|syslog_badpri|syslog_goodpri|timestampdir|timestampowner|secure_path/ = /[^\001-\004\t\n "#,=\\]+|"[^\001-\004\n"#,=\\]+"/ }
      | { /((exempt_group|lecture|lecture_file|listpw|logfile|mailerflags|mailerpath|mailto|mailfrom|syslog|verifypw))|((exempt_group|lecture|lecture_file|listpw|logfile|mailerflags|mailerpath|mailto|mailfrom|syslog|verifypw))/ = /(([^\001-\004\t\n "#,=\\]+|"[^\001-\004\n"#,=\\]+"))/ }
      | { /((env_check|env_delete|env_keep))|((env_check|env_delete|env_keep))/ })*
    ({ /#comment/ = /[^\001-\004\t\n\r ][^\001-\004\n]*[^\001-\004\t\n\r ]|[^\001-\004\t\n\r ]/ }
      | ())
  with tree
    { "type" = ":testuser" } { "syslog" } { "log_output" }
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/sudoers.aug:432.17-433.52:

Error in /etc/grub.conf:1.0 (parse_failed)
  Get did not match entire input
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/grub.aug:285.14-286.43:

Error in /etc/modprobe.d/unsupported-modules:10.0 (parse_failed)
  Iterated lens matched less than it should
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/modprobe.aug:103.10-.32:
    Last matched: /opt/puppetlabs/puppet/share/augeas/lenses/dist/util.aug:134.6-.14:

Error in /etc/modprobe.conf:305.0 (parse_failed)
  Iterated lens matched less than it should
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/modprobe.aug:103.10-.32:
    Last matched: /opt/puppetlabs/puppet/share/augeas/lenses/dist/util.aug:134.6-.14:

Error in /etc/inputrc:114.0 (parse_failed)
  Syntax error
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/inputrc.aug:52.10-.69:

Error in /etc/host.conf:11.11 (parse_failed)
  Iterated lens matched less than it should
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/host_conf.aug:66.10-.48:
    Last matched: /opt/puppetlabs/puppet/share/augeas/lenses/dist/build.aug:59.43-.57:
    Next (no match): /opt/puppetlabs/puppet/share/augeas/lenses/dist/util.aug:54.12-.31:

Error in /etc/rsyslog.conf:26.0 (parse_failed)
  Get did not match entire input
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/rsyslog.aug:61.10-.57:

Error in /boot/grub/menu.lst:7.0 (parse_failed)
  Get did not match entire input
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/grub.aug:285.14-286.43:

Error in /boot/grub/grub.conf:7.0 (parse_failed)
  Get did not match entire input
  Lens: /opt/puppetlabs/puppet/share/augeas/lenses/dist/grub.aug:285.14-286.43: