added regression test for https://github.com/pythonnet/pythonnet/issu…

added regression test for https://github.com/pythonnet/pythonnet/issu… · pythonnet/pythonnet@d975d5f

Original file line number	Diff line number	Diff line change
`@@ -290,3 +290,19 @@ def __init__(self, i, s):`
`290`	`290`	`assert len(calls) == 1`
`291`	`291`	`assert calls[0][0] == 1`
`292`	`292`	`assert calls[0][1] == "foo"`
	`293`	`+`
	`294`	`+# regression test for https://github.com/pythonnet/pythonnet/issues/1565`
	`295`	`+def test_can_be_collected_by_gc():`
	`296`	`+from Python.Test import BaseClass`
	`297`	`+`
	`298`	`+class Derived(BaseClass):`
	`299`	`+__namespace__ = 'test_can_be_collected_by_gc'`
	`300`	`+`
	`301`	`+inst = Derived()`
	`302`	`+cycle = [inst]`
	`303`	`+del inst`
	`304`	`+cycle.append(cycle)`
	`305`	`+del cycle`
	`306`	`+`
	`307`	`+import gc`
	`308`	`+gc.collect()`