* YesssSMS handling more errors, upgrade to version 0.2.1

 - handling missing internet connection nicely
 - disabling login with non-working credentials (website locked account for 1 hour)
 - upgrade to new upstream version of YesssSMS

* notify.yessssms tests

* test requirements

* flake8 fix

* fixing tests, new upstream version 0.2.3

fixing tests based on requested changes, coverage

* removing unmotivated print

* passing exception to ConnectionError and SMSSendingError logger