[UI] MAAS should handle better errors in curtin preseeds

MAAS curtin preseed should be rendering the curtin_userdata file correctly, and not assuming that the user will use the correct encoding. From the user perspective, this should all be 'str' and not 'byte-encoded'.

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/lib/python3/dist-packages/maasserver/utils/views.py", line 180, in view_atomic_with_post_commit_savepoint
    return view_atomic(*args, **kwargs)
  File "/usr/lib/python3.5/contextlib.py", line 30, in inner
    return func(*args, **kwds)
  File "/usr/lib/python3/dist-packages/maasserver/api/support.py", line 54, in __call__
    response = upcall(request, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/django/views/decorators/vary.py", line 21, in inner_func
    response = func(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/piston3/resource.py", line 190, in __call__
    result = self.error_handler(e, request, meth, em_format)
  File "/usr/lib/python3/dist-packages/piston3/resource.py", line 188, in __call__
    result = meth(request, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/maasserver/api/support.py", line 202, in dispatch
    return function(self, request, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/metadataserver/api.py", line 681, in read
    user_data = get_curtin_userdata(node)
  File "/usr/lib/python3/dist-packages/maasserver/preseed.py", line 269, in get_curtin_userdata
    configs=get_curtin_yaml_config(node),
  File "/usr/lib/python3/dist-packages/maasserver/preseed.py", line 216, in get_curtin_yaml_config
    main_config = get_curtin_config(node)
  File "/usr/lib/python3/dist-packages/maasserver/preseed.py", line 342, in get_curtin_config
    return template.substitute(**context)
  File "/usr/lib/python3/dist-packages/tempita/__init__.py", line 173, in substitute
    result, defs, inherit = self._interpret(ns)
  File "/usr/lib/python3/dist-packages/tempita/__init__.py", line 184, in _interpret
    self._interpret_codes(self._parsed, ns, out=parts, defs=defs)
  File "/usr/lib/python3/dist-packages/tempita/__init__.py", line 212, in _interpret_codes
    self._interpret_code(item, ns, out, defs)
  File "/usr/lib/python3/dist-packages/tempita/__init__.py", line 218, in _interpret_code
    self._exec(code[2], ns, pos)
  File "/usr/lib/python3/dist-packages/tempita/__init__.py", line 320, in _exec
    raise exc_info[0](e).with_traceback(exc_info[2])
  File "/usr/lib/python3/dist-packages/tempita/__init__.py", line 312, in _exec
    exec(code, self.default_namespace, ns)
  File "<string>", line 7, in <module>
TypeError: a bytes-like object is required, not 'str' at line 2 column 3 in file /etc/maas/preseeds/curtin_userdata

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I have a MAAS server running Xenial and MAAS 1.10 from maas/next. The server has 14.04 images from the Release stream.

On the node, there are three NICs and all three are set to AutoAssign and are assigned 10.0.0.125, 126 and 127.

On boot, the installer ephemeral boots but then cloud-init tries to get data from 169.254.169.254. It does this for 120 seconds, THEN tries calling 10.0.0.1 which also fails, and then it finally just gives up.

At this point, the node is up, and stuck and I had to backdoor it to get logs.

The logs are attached from the node, the biggest thing I noticed was this:

2016-02-22 16:50:25,132 - util.py[WARNING]: Failed fetching metadata from url http://10.0.0.1/MAAS/metadata/curtin
2016-02-22 16:50:25,133 - util.py[DEBUG]: Failed fetching metadata from url http://10.0.0.1/MAAS/metadata/curtin
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/cloudinit/sources/DataSourceMAAS.py", line 84, in get_data
    paths=self.paths)
  File "/usr/lib/python2.7/dist-packages/cloudinit/sources/DataSourceMAAS.py", line 236, in read_maas_seed_url
    ssl_details=ssl_details)
  File "/usr/lib/python2.7/dist-packages/cloudinit/util.py", line 704, in read_file_or_url
    exception_cb=exception_cb)
  File "/usr/lib/python2.7/dist-packages/cloudinit/url_helper.py", line 257, in readurl
    raise excps[-1]
UrlError: 500 Server Error: INTERNAL SERVER ERROR

However, when I try that metadata, after getting in via the backdoor, it seems to work:

backdoor@ubuntu:~$ echo $url
http://10.0.0.1/MAAS/metadata/curtin
backdoor@ubuntu:~$ sudo python $maasds --config=$cfg get $url
== http://10.0.0.1/MAAS/metadata/curtin ==
2012-03-01
latest

backdoor@ubuntu:~$ sudo python $maasds --config=$cfg crawl $url/latest/meta-data/
== http://10.0.0.1/MAAS/metadata/curtin/latest/meta-data/instance-id ==
node-9c831f44-d6b9-11e5-8cc4-eca86bfb9f66

== http://10.0.0.1/MAAS/metadata/curtin/latest/meta-data/local-hostname ==
x-wing.maas

== http://10.0.0.1/MAAS/metadata/curtin/latest/meta-data/public-keys ==
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQD0UpxLhAfnGngLGdgK720nezbgSKgYfV8WyNA4f2X6ATtMEt28Kx7UdO4udhBeINbHlfNrt9ddm+VrKC4MhPGeKLna71IKu07UUbZVWz0kHd8+gwpeoc7VA8p02ZSbXcXBSLhDBEWa8ly2opmuFvs6jG2UdusAUe2ooskTL+itRE68QBD2um90MgbmM5efYayGX97c++0ogxM21osSjpapiJrXap2zUDolq0IDVQA0YujyGw85BgojmuaSvLDvnynic610Ogkrd00TSAniZ8h18C5xZur8Ex1yfa/p4h87AH/Equ0fblbSxJkhP59HUnYiaUvGJ3JXb4YQcEX2UJMb bladernr@critical-maas

== http://10.0.0.1/MAAS/metadata/curtin/latest/meta-data/x509 ==

backdoor@ubuntu:~$ sudo python $maasds --config=$cfg crawl $url/2012-03-01/meta-data/
== http://10.0.0.1/MAAS/metadata/curtin/2012-03-01/meta-data/instance-id ==
node-9c831f44-d6b9-11e5-8cc4-eca86bfb9f66

== http://10.0.0.1/MAAS/metadata/curtin/2012-03-01/meta-data/local-hostname ==
x-wing.maas

== http://10.0.0.1/MAAS/metadata/curtin/2012-03-01/meta-data/public-keys ==
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQD0UpxLhAfnGngLGdgK720nezbgSKgYfV8WyNA4f2X6ATtMEt28Kx7UdO4udhBeINbHlfNrt9ddm+VrKC4MhPGeKLna71IKu07UUbZVWz0kHd8+gwpeoc7VA8p02ZSbXcXBSLhDBEWa8ly2opmuFvs6jG2UdusAUe2ooskTL+itRE68QBD2um90MgbmM5efYayGX97c++0ogxM21osSjpapiJrXap2zUDolq0IDVQA0YujyGw85BgojmuaSvLDvnynic610Ogkrd00TSAniZ8h18C5xZur8Ex1yfa/p4h87AH/Equ0fblbSxJkhP59HUnYiaUvGJ3JXb4YQcEX2UJMb bladernr@critical-maas

== http://10.0.0.1/MAAS/metadata/curtin/2012-03-01/meta-data/x509 ==