(MODULES-2892) Handle missing file in file_line

[silug]

In noop mode, file_line should not fail if the file does not exist.

MODULES-2892 #close

[CLAassistant]

All committers have signed the CLA.

[silug]

Without this change:

$ puppet apply -e 'file { "/tmp/no_such_file": ensure => present } -> file_line { "foo": ensure => present, path => "/tmp/no_such_file", line => "foo" }' --modulepath spec/fixtures/modules --noop
Notice: Compiled catalog for localhost in environment production in 0.02 seconds
Notice: /Stage[main]/Main/File[/tmp/no_such_file]/ensure: current_value 'absent', should be 'present' (noop)
Error: /Stage[main]/Main/File_line[foo]: Could not evaluate: No such file or directory @ rb_sysopen - /tmp/no_such_file
Notice: Applied catalog in 0.01 seconds

With the change:

$ puppet apply -e 'file { "/tmp/no_such_file": ensure => present } -> file_line { "foo": ensure => present, path => "/tmp/no_such_file", line => "foo" }' --modulepath spec/fixtures/modules --noop
Notice: Compiled catalog for localhost in environment production in 0.02 seconds
Notice: /Stage[main]/Main/File[/tmp/no_such_file]/ensure: current_value 'absent', should be 'present' (noop)
Notice: /Stage[main]/Main/File_line[foo]/ensure: current_value 'absent', should be 'present' (noop)
Notice: Class[Main]: Would have triggered 'refresh' from 2 events
Notice: Stage[main]: Would have triggered 'refresh' from 1 event
Notice: Applied catalog in 0.01 seconds

[ekohl]

Slight nit on coding style, otherwise 👍

[ekohl]

Looks good to me. I started the tests. Please ping if I (or some other maintainer) forgets to check back and merge.