Preparatory work to improve .isolate global variables management.

Preparatory work to improve .isolate global variables management.

Remove access from non clients to Configs._by_config and add a default global
variables by default. Add asserts in the process to ensure I don't mess up
again.

R=csharp@chromium.org
BUG=

Committed: https://code.google.com/p/swarming/source/detail?repo=client&r=8170f49

[M-A, 2014-03-13 01:01:11]

No functional change (yet).

[csharp, 2014-03-13 18:13:10]

https://codereview.appspot.com/75160043/diff/20001/isolate_format.py
File isolate_format.py (right):

https://codereview.appspot.com/75160043/diff/20001/isolate_format.py#newcode613
isolate_format.py:613: Takes the first file comment, prefering lhs.
Strange wording, maybe "Take lhs file comment if available, otherwise take from
rhs"

https://codereview.appspot.com/75160043/diff/20001/isolate_format.py#newcode615
isolate_format.py:615: # At that point, we need to merge the keys. By default,
all the new
At what point? I think you can just remove that part of the comment.

https://codereview.appspot.com/75160043/diff/20001/isolate_format.py#newcode624
isolate_format.py:624: # pylint: disable=W0212
What is this disabling now?

[M-A, 2014-03-13 19:05:17]

https://codereview.appspot.com/75160043/diff/20001/isolate_format.py
File isolate_format.py (right):

https://codereview.appspot.com/75160043/diff/20001/isolate_format.py#newcode613
isolate_format.py:613: Takes the first file comment, prefering lhs.
On 2014/03/13 18:13:10, csharp1 wrote:
> Strange wording, maybe "Take lhs file comment if available, otherwise take
from
> rhs"

Fixed.

https://codereview.appspot.com/75160043/diff/20001/isolate_format.py#newcode615
isolate_format.py:615: # At that point, we need to merge the keys. By default,
all the new
On 2014/03/13 18:13:10, csharp1 wrote:
> At what point? I think you can just remove that part of the comment.

Done.

https://codereview.appspot.com/75160043/diff/20001/isolate_format.py#newcode624
isolate_format.py:624: # pylint: disable=W0212
On 2014/03/13 18:13:10, csharp1 wrote:
> What is this disabling now?

Sadly, with rhs._by_config pylint is confused about the type of rhs and doesn't
know it is the same type as the class. So I have to keep the warning disabled.

[csharp, 2014-03-13 19:06:27]

lgtm

[M-A, 2014-03-13 19:27:02]

Committed patchset #3 manually as r8170f49 (presubmit successful).