Fix refcnt errors (split from #958)#1001

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filmor merged 4 commits intopythonnet:masterfrom

amos402:fix-refcnt-errors

Dec 2, 2019

Commits on Nov 27, 2019

Add exception helper
amos402
committed

Commits on Nov 28, 2019

Commits on Nov 30, 2019

Fix refcnt error by using `using`
amos402
committed