typing: minimal changes to make a no-op mypy run pass

a few notes on these mypy adaptations, probably the most complicated thus far for an almost no-op run:

• some lines got overlong, most notably due to the Union[AbstractAttribute, ...] cases. They will get much nicer looking with Python 3.7, as we will then be able to anticipate the type annotation and get rid of "type: ". The line breaks will also be nicer

• the default_min_bound attribute is really used in a type-inconsistent way, sometime it's a string, sometime a datetime, sometime an integer, etc. That calls for a better interface/abstraction, but I wanted to be minimal here, so I just typed it Any for now

Test Plan

tox -e mypy

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Migrated from D2123 (view on Phabricator)

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• mypy: use sqlalchemy plugin

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I've marked this as depending on !107 (closed), as the encoding fix for the CRAN lister (formerly known as !111 (closed)) has been integrated there.

I also prefer the new line-breaking style, there's less space wasted by indentations

Merge request was accepted

approved this merge request

! In !110 (closed), @vlorentz wrote: I also prefer the new line-breaking style, there's less space wasted by indentations

I don't understand what you mean here, and whether you're suggesting a better way of breaking lines right now (or with Python >= 3.6). Can you elaborate?

This will need a rebase though.

updating !110 (closed)

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• typing: minimal changes to make a no-op mypy run pass
• CRAN lister: make shelling out decoding compatible with Python 3.5

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• typing: minimal changes to make a no-op mypy run pass
• CRAN lister: make shelling out decoding compatible with Python 3.5
• mypy: add typing annotations for novel lister abstractions

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• CRAN lister: fix compute_package_url interpolation

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• typing: minimal changes to make a no-op mypy run pass
• CRAN lister: make shelling out decoding compatible with Python 3.5
• mypy: add typing annotations for novel lister abstractions
• CRAN lister: fix compute_package_url interpolation

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