Ensure all the exceptions cat be spied on

This change replaces `Exception` with `BaseException` in the `spy()`
method provided by the `mocker` fixture. This enables the caller to
spy on things like `KeyboardInterrupt`, `GeneratorExit` and
`SystemExit` exceptions that hasn't been possible before because of
a bug.

Before this change, any occurances of the above exceptions caused
`spy()` to assign `None` to both `spy_return` and `spy_exception`
attributes.

Fixes pytest-dev#215

src/pytest_mock/plugin.py

@@ -114,7 +114,7 @@ def wrapper(*args, **kwargs):
             spy_obj.spy_exception = None
             try:
                 r = method(*args, **kwargs)
-            except Exception as e:
+            except BaseException as e:
                 spy_obj.spy_exception = e
                 raise
             else:
@@ -126,7 +126,7 @@ async def async_wrapper(*args, **kwargs):
             spy_obj.spy_exception = None
             try:
                 r = await method(*args, **kwargs)
-            except Exception as e:
+            except BaseException as e:
                 spy_obj.spy_exception = e
                 raise
             else:

tests/test_pytest_mock.py

@@ -2,7 +2,7 @@
 import platform
 import sys
 from contextlib import contextmanager
-from typing import Callable, Any, Tuple, Generator
+from typing import Callable, Any, Tuple, Generator, Type
 from unittest.mock import MagicMock
 
 import pytest
@@ -235,17 +235,32 @@ def bar(self, arg):
     assert spy.spy_return == 20
 
 
-def test_instance_method_spy_exception(mocker: MockerFixture) -> None:
+# Ref: https://docs.python.org/3/library/exceptions.html#exception-hierarchy
+@pytest.mark.parametrize(
+    'exc_cls',
+    (
+        BaseException,
+        Exception,
+        GeneratorExit,  # BaseException
+        KeyboardInterrupt,  # BaseException
+        RuntimeError,  # regular Exception
+        SystemExit,  # BaseException
+    )
+)
+def test_instance_method_spy_exception(
+        exc_cls: Type[BaseException],
+        mocker: MockerFixture,
+) -> None:
     class Foo:
         def bar(self, arg):
-            raise Exception("Error with {}".format(arg))
+            raise exc_cls("Error with {}".format(arg))
 
     foo = Foo()
     spy = mocker.spy(foo, "bar")
 
     expected_calls = []
     for i, v in enumerate([10, 20]):
-        with pytest.raises(Exception, match="Error with {}".format(v)) as exc_info:
+        with pytest.raises(exc_cls, match="Error with {}".format(v)) as exc_info:
             foo.bar(arg=v)
 
         expected_calls.append(mocker.call(arg=v))