[telemetry] Move stale .pyc check from Python import to gclient hook.

[telemetry] Move stale .pyc check from Python import to gclient hook.

This check turns out to be fairly expensive on Windows (~150ms), and having
it at import time means we're taking the hit every time we launch
memory_cache_http_server. We only need to do this if the Python files have
changed, so move it to runhooks.

The reason this check exists in the first place is that we've had problems in
the past where e.g. someone renames foo.py to foo/__init__.py. foo.pyc remains
on the filesystem of every Chromium checkout and causes a name conflict in
Python imports - foo can refer to the compiled module or the package.


BUG=388256
TEST=git rm a file in src/tools that has a .pyc; git commit; gclient runhooks; ensure .pyc doesn't exist; undo commit

Committed: https://crrev.com/94f4bd9c8bf1ab611a41b290e8feb1d48fdb1f21
Cr-Commit-Position: refs/heads/master@{#291825}

[dtu, 2014-08-20 00:54:49]

Dirk, do you know how to test something like this? In particular, I'm not sure
if the DEPS pattern follows the correct format.

Also, if there's a way to reference the matching files, we can limit this check
to only those?

[Dirk Pranke, 2014-08-20 01:02:23]

I think you can probably test this by moving or deleting a file locally and then
running 'gclient runhooks'.

Or, as part of this patch, rename a file and run a try job against that (then
undo the rename before you're ready to land things).

https://codereview.chromium.org/489693002/diff/20001/DEPS
File DEPS (right):

https://codereview.chromium.org/489693002/diff/20001/DEPS#newcode839
DEPS:839: "pattern": "src/tools/.\\.py",
I think you probably want "src/tools/.*\\.py" here.

[dtu, 2014-08-25 23:57:53]

Patchset #4 (id:60001) has been deleted

[dtu, 2014-08-25 23:58:30]

The CQ bit was checked by dtu@chromium.org

[commit-bot: I haz the power, 2014-08-26 00:01:46]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dtu@chromium.org/489693002/80001

[commit-bot: I haz the power, 2014-08-26 00:01:47]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-08-26 00:01:48]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[tonyg, 2014-08-26 00:03:25]

lgtm

[dtu, 2014-08-26 00:06:33]

The CQ bit was checked by dtu@chromium.org

[commit-bot: I haz the power, 2014-08-26 00:09:31]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dtu@chromium.org/489693002/80001

[commit-bot: I haz the power, 2014-08-26 03:02:23]

Committed patchset #4 (80001) as 12fdb8797b334a744a5cc4cc0f6f40f2c84c7a1f

[commit-bot: I haz the power, 2014-09-10 02:39:52]

Patchset 4 (id:??) landed as
https://crrev.com/94f4bd9c8bf1ab611a41b290e8feb1d48fdb1f21
Cr-Commit-Position: refs/heads/master@{#291825}