snapcraft.yaml validation errors report the line number starting from 0

[Leo Arias]

When there is a validation error in the snapcraft.yaml, it prints the line number. That line number is off-by-one because it starts indexing in 0.

To reproduce, get the attached yaml and run snapcraft:

$ snapcraft
Issues while validating snapcraft.yaml: found character '\t' that cannot start any token on line 7 of snapcraft.yaml

$ cat -n snapcraft.yaml
1 name: my-snap # the name of the snap
2 version: 0 # the version of the snap
3 summary: This is my-snap's summary # 79 char long summary
4 description: This is my-snap's description # a longer description for the snap
5 confinement: devmode # use "strict" to enforce system access only via declared interfaces
6
7 parts:
8 my-part: # line with \t
9 plugin: nil

The error is in my-part, line 8.

[Leo Arias (elopio)]

Here's an example of +1 the mark: http://pyyaml.org/wiki/PyYAMLDocumentation#YAMLError

[Sergio Schvezov (sergiusens)]

https://github.com/snapcore/snapcraft/pull/816