Fix AttributeError for Elasticsearch>2.0.0,<3.0.0

[artemknd]

AIOHttpConnection takes use_ssl argument and passes one to the parent's init.

Then self.use_ssl gets used instead of use_ssl here
https://github.com/aio-libs/aioelasticsearch/blob/master/aioelasticsearch/connection.py#L52

It works for the latest elasticsearch-py versions, however, it doesn't work with >2.0.0, b/c there's no self.use_ssl = use_ssl there.

What do these changes do?

Are there changes in behavior for the user?

Related issue number

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
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[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 0.23%. Comparing base (26fcd7c) to head (baa68ef).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
aioelasticsearch/connection.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##           master    #197   +/-   ##
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  Coverage    0.23%   0.23%           
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  Files           6       6           
  Lines         433     433           
  Branches       77      77           
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  Hits            1       1           
  Misses        432     432           

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[asvetlov]

Is elasticsearch 2.x supported still?

[artemknd]

@asvetlov I tested out search and scan aioelasticsearch examples.
They both work for ES 2.x with my tiny fix.

As for elasticsearch-py, 2.X is supported as well
https://github.com/elastic/elasticsearch-py#compatibility

[asvetlov]

Manual testing is not enough; the library should be tested by travis-ci against all supported ES versions.
ES_TAG env var already exists in .travis.yml config file, I'm ok with adding the travis matrix for testing several versions.
Sorry, I have no time/motivation for making the fix myself but happy to review a PR from a champion.
Please note: extending the matrix requires a separate PR.

[artemknd]

@asvetlov did you have a chance to take a look at the code itself?

The update is very straightforward. I just substituted referred parent class's Connection property self.use_ssl with constructor's argument use_ssl directly.

I'd even say it's quite reasonable and makes more sense, b/c there's no dependency on the underlying parent's implementation.

Current tests are all good. So, I believe it's safe to merge one.
Could you take a look at the code diff and merge it, please?

[asvetlov]

Please don't get me wrong.
You are asking for changing the code that works fine already according to the current test suite.
There is no reason to do it, even if the change is barely minimal.
My motivation for hesitation is a chance to break something by accident. Don't fix if not broken, test the fix of broken things.

You said that the PR fixes ES 2.x, that's awesome!
What I'm asking is adding a test to check this (and to make sure that the lastest aioelasticsearch works with ES 2.x at all). It can be done easily by extending travis config matrix.
Could you update it?