Invalid write_files format doesn't make the cloud-init fail

This bug was originally filed in Launchpad as [LP: #1867933](https://bugs.launchpad.net/cloud-init/+bug/1867933)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2020-03-18T14:25:16.396575+00:00

date_fix_committed = None

date_fix_released = None

id = 1867933

importance = medium

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1867933

milestone = None

owner = boillodmanuel

owner_name = manuel

private = False

status = confirmed

submitter = boillodmanuel

submitter_name = manuel

tags = []

duplicates = []

_Launchpad user **manuel(boillodmanuel)** wrote on 2020-03-18T14:25:16.396575+00:00_

If the cloud config file format is not correct (see example below), the write_files module fails, but the cloud-init status is done

Cloud-config file:

```
#cloud-config

write_files:
- content: |
line below is badly indented
ouch!

path: /tmp/cloud-init-file.txt
```

Extract of cloud-init-output.log
```
2020-03-18 13:54:05,321 - util.py[WARNING]: Failed loading yaml blob. Invalid format at line 6 column 1: "while scanning a simple key
in "", line 6, column 1:
ouch!
^
could not found expected ':'
in "", line 8, column 9:
path: /tmp/cloud-init-file.txt
^"
2020-03-18 13:54:05,337 - util.py[WARNING]: Failed loading yaml blob. Invalid format at line 6 column 1: "while scanning a simple key
in "", line 6, column 1:
ouch!
^
could not found expected ':'
in "", line 8, column 9:
path: /tmp/cloud-init-file.txt
^"
2020-03-18 13:54:05,337 - util.py[WARNING]: Failed at merging in cloud config part from part-001
```

cloud-init status:
```
status: done
```