Close transport when fetching the schema failed

[joricht]

Fetching the schema from the transport might fail with an exception. This Commit
ensures that the transport is closed in such a case and the client object can be
used to open a new session.

[leszekhanusz]

Thanks for your PR!

Could you please also add two tests for sync and async ?

[joricht]

@leszekhanusz Thank you for the quick reply and review. I am on holiday over the weekend and will address everything on Monday.

[joricht]

@leszekhanusz I added two tests and a comment why I catch the broad exception. Can you have a look at it again. Thank you!

[leszekhanusz]

Thanks. Please read the CONTRIBUTING.md file to see how to fix linter errors (running make check)

[joricht]

@leszekhanusz Thanks for being so patient. Now all tests should pass and the coding guidelines are also respected.

[codecov-commenter]

Codecov Report

Merging #297 (18fead4) into master (12fc895) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #297   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           26        26           
  Lines         2060      2068    +8     
=========================================
+ Hits          2060      2068    +8     

Impacted Files	Coverage Δ
gql/client.py	100.00% <100.00%> (ø)

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[leszekhanusz]

LGTM 🚀