Make Click context optional to be able to call functions from an external module

Problem

Since Click migration (v0.7.0), It is not possible to use a function which internally make a request. For external usage and tests without Click is not possible.

EndPoint class is coupled with Click context pass_context for custom endpoint or GTEST usage for BMA api string generation.

Would allow

• Write tests which requires requests is not possible (most of the tests)
• @tuxmain to use the transaction functions for ĞMixer and other projects to take advantages of Silkaj code.

Solution

In EndPoint class:

• Use RuntimeError to detect that there is no Click context in case Click is installed and loaded
• Use ModuleNotFoundError in case Click is not installed
• Previous point requires Python ≥ 3.6, and I didn’t found a way to import it with __future__ for Python 3.5 support.
• To keep Python 3.5 support, I can just check for general exception for now. And, when Silkaj will drop Python 3.5, we could add back ModuleNotFoundError exception.

Test

• Test EndPoint().BMA_ENDPOINT with click context
• Test EndPoint().BMA_ENDPOINT without click context
• Figure out how to test a singleton function
• Test with Python 3.5: Not found how to simulate missing module

After

• Write test_tx_history_generate_table() test.