Fix misleading log message for aria-current="true"

[feerrenrut]

Link to issue number:

None

Summary of the issue:

There is a misleading log message for aria-current="true". It was a non-handled value, an exception was raised, a message added to the log, and the value True (bool rather than str) was used.

When trying to follow this code it is hard to know where the values are strings, None, or bool. In some cases the naming is overly specific.

Description of how this pull request fixes the issue:

Types and naming for isCurrent were confusing, so normalize the types
using an enum and only name as ariaCurrent when the data is specific to aria-current,
otherwise use 'isCurrent'. Include comments to link aria-current as the
potential (likely) source for 'isCurrent'

Testing performed:

Used Chrome, Firefox, IE, and Edge with https://a11ysupport.io/tests/html/aria/aria-current.html

Known issues with pull request:

This is technically an API breaking change. If there are any concerns about this, we may have to wait for the 2021.1 release.

Change log entry:

changes for developers:
- 'NVDAObject' (and derivatives) property 'isCurrent' now strictly returns 'controlTypes.IsCurrent'. It is no longer Optional, and thus will not return None. When an object is not current 'controlTypes.IsCurrent.NO' is returned.
- The 'controlTypes.isCurrentLabels' has been removed, instead use the 'displayString' property on a 'controlTypes.IsCurrent' enum value. EG 'controlTypes.IsCurrent.YES.displayString'

[feerrenrut]

@LeonarddeR I have addressed your suggestions. I think making this a property is a good idea. I decided against translation because it is hard to search for usages in the code base. Instead I have gone with displayString which communicates that it is for displaying to the user. This also leaves room for other transformations (other than translation) to happen to this string prior to being presented to a user.

[LeonarddeR]

Great @feerrenrut

[feerrenrut]

I have just noticed inconsistent case for IsCurrent.Yes all the rest of the values are uppercase. I'll fix this.

[feerrenrut]

Python docs for enum use upper case for members of the enum, so I'll match that style.

[AppVeyorBot]

• Build (for testing PR)
• System test failure

See test results for failed build of commit afe27d9a62

[AppVeyorBot]

• PR introduces Flake8 errors
• Build (for testing PR)

See test results for failed build of commit 66cf02e9be