Consistent Module Imports

[PaulTalbot-INL]

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Issue Description

What did you expect to see happen?

Consistent, modular imports throughout RAVEN

What did you see instead?

Fiddling with PYTHONPATH and some inconsistency in when some modules can import others safely, as well as occasional imports in the body of python modules

Do you have a suggested fix for the development team?

We should probably continue towards making RAVEN more library-like, so that our imports all happen in a consistent way.

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For Devs: Issue Review

• 1. Is it tagged with a type: defect or improvement? tagged
• 2. Is it tagged with a priority: critical, normal or minor? tagged
• 3. If it will impact requirements or requirements tests, is it tagged with requirements? n/a
• 4. If it is a defect, can it cause wrong results for users? If so an email needs to be sent to the users. n/a
• 5. Is a rationale provided? (Such as explaining why the improvement is needed or why current code is wrong.) provided

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For Devs: Issue Closure

• 1. If the issue is a defect, is the defect fixed?
• 2. If the issue is a defect, is the defect tested for in the regression test system? (If not explain why not.)
• 3. If the issue can impact users, has an email to the users group been written (the email should specify if the defect impacts stable or master)?
• 4. If the issue is a defect, does it impact the latest stable branch? If yes, is there any issue tagged with stable (create if needed)?
• 5. If the issue is being closed without a merge request, has an explanation of why it is being closed been provided?

[joshua-cogliati-inl]

Note that when this is fixed, we can probably add some useful checks to the pylint checks in developer_tools/pylint_list and developer_tools/pylint_check