Change implicit relative import and add ana test

[gerritholl]

Change an implicit to an explicit relative import in the ana runner and add a rudimentary unit test for the runner. Also replaced two calls to logger.error by logger.exception as it was printing insufficient information for the exception before.

• [x] Fixes #12
• [x] Tests added
• [x] Tests passed

[ghost]

DeepCode's analysis on #22d23d found:

• :information_source: 3 minor issues. :point_down:
• :heavy_check_mark: 1 issue was fixed.

  Top issues

Description	Example fixes
Undefined variable 'breakpoint' Occurrences: test_ana.py:63	:wrench: Example fixes
Either all return statements in a function should return an expression, or none of them should. Occurrences: test_ana.py:50	:wrench: Example fixes
Use % formatting in logging functions and pass the % parameters as arguments Occurrences: do_ana_correction.py:90 do_ana_correction.py:160	:wrench: Example fixes

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[gerritholl]

Can a member of @pytroll/core please assign @TAlonglong as a reviewer here?