* Use py3's f-strings instead of s.format(**locals())
In light of the bug reported here
https://github.com/apache/incubator-superset/issues/6347, which seems
like an odd `.format()` issue in py3, I greped and replaced all
instances of `.format(**locals())` using py3's f-strings
* lint
* fix tests
* [utils] gathering/refactoring into a "utils/" folder
Moving current utils.py into utils/core.py and moving other *util*
modules under this new "utils/" as well.
Following steps include eroding at "utils/core.py" and breaking it down
into smaller modules.
* Improve tests
* Make loading examples in scope for tests
* Remove test class attrs examples_loaded and requires_examples
* [bugfix] temporal columns with expression fail
error msg: "local variable 'literal' referenced before assignment"
Error occurs [only] when using temporal column defined as a SQL
expression.
Also noticed that examples were using `granularity` instead of using
`granularity_sqla` as they should. Fixed that here.
* Add tests
* Add "Impersonate user" setting to Datasource
* Add tests
* Use g.user.username for all the sync cases
* use uri.username instead of uri.user
* Small refactoring
Maxime Beauchemin
timifasubaa
michellethomas
John Bodley
Dmitry Goryunov
Sungju Jin