Merge ~powersj/cloud-init:fix-arch-hostname into cloud-init:master

[Joshua Powers]

archlinux: fix set hostname

cloud-init fails to set the hostname on Arch Linux becuase that
_write_hostname passes conf instead of str(conf) to util.write_file.

LP: #1705306

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:7cb9df67d9820fa7e885e82dfbe0d5ba62bd58da
https://jenkins.ubuntu.com/server/job/cloud-init-ci/79/
Executed test runs:
    SUCCESS: Checkout
    SUCCESS: Unit & Style Tests
    SUCCESS: Ubuntu LTS: Build
    SUCCESS: Ubuntu LTS: Integration
    SUCCESS: CentOS 6 & 7: Build & Test
    IN_PROGRESS: Declarative: Post Actions

Click here to trigger a rebuild:
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review: Approve (continuous-integration)

[Scott Moser (smoser)]

summary: add 'omode' to the write_file call
  util.write_file(out_fn, str(conf), mode=0o644, omode="w")

Reasoning:
write_file does an 'open' by default with 'wb' (binary mode).
The, if the mode is binary, it will try to encode the contents which is why
we see the failure.

Your change works because you're passing a string now, which *does* have
.encode(), but it'd be better to avoid write_file's magic and pass a
string as well as open in string mode so no .encode() or .decode() had
to happen.

in its calls to 'encode_text' or 'decode_text', write_file is doing more magic
then it should. Ultimately it'd be better if the caller provided correct
modes and data, which is what we're doing here.

review: Needs Fixing

[Scott Moser (smoser)]

I'm just going to make that under your name, and pull it..

review: Approve

diff --git a/cloudinit/distros/arch.py b/cloudinit/distros/arch.py
index 75d4620..8a9c359 100644
--- a/cloudinit/distros/arch.py
+++ b/cloudinit/distros/arch.py
@@ -119,7 +119,7 @@ class Distro(distros.Distro):
         if not conf:
             conf = HostnameConf('')
         conf.set_hostname(your_hostname)
-        util.write_file(out_fn, conf, 0o644)
+        util.write_file(out_fn, str(conf), 0o644)
 
     def _read_system_hostname(self):
         sys_hostname = self._read_hostname(self.hostname_conf_fn)