tests/basics: Split out gen throw tests from yield-from-throw tests.

tests/basics/generator_throw.py

@@ -0,0 +1,43 @@
+# case where generator doesn't intercept the thrown/injected exception
+def gen():
+    yield 123
+    yield 456
+        
+g = gen()
+print(next(g))
+try:
+    g.throw(KeyError)
+except KeyError:
+    print('got KeyError from downstream!')
+
+# case where a thrown exception is caught and stops the generator
+def gen():
+    try:
+        yield 1
+        yield 2
+    except:
+        pass
+g = gen()
+print(next(g))
+try:
+    g.throw(ValueError)
+except StopIteration:
+    print('got StopIteration')
+
+# generator ignores a thrown GeneratorExit (this is allowed)
+def gen():
+    try:
+        yield 123
+    except GeneratorExit:
+        print('GeneratorExit')
+    yield 456
+        
+# thrown a class
+g = gen()
+print(next(g))
+print(g.throw(GeneratorExit))
+
+# thrown an instance
+g = gen()
+print(next(g))
+print(g.throw(GeneratorExit()))