Fix btbsession and integration tests

[pvk-developer]

Resolve #175

[codecov-io]

Codecov Report

Merging #174 into master will increase coverage by 0.13%.
The diff coverage is 96.55%.

@@            Coverage Diff            @@
##           master    #174      +/-   ##
=========================================
+ Coverage   96.36%   96.5%   +0.13%     
=========================================
  Files          39      39              
  Lines        1017    1029      +12     
=========================================
+ Hits          980     993      +13     
+ Misses         37      36       -1

Impacted Files	Coverage Δ
btb/tuning/__init__.py	100% <100%> (ø)	⬆️
btb/session.py	96.66% <96.42%> (+0.98%)	⬆️

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