## What changes were proposed in this pull request?
This particular test is being skipped at PyPy and Python 2.
```
Skipped tests in pyspark.sql.tests.test_context with pypy:
test_unbounded_frames (pyspark.sql.tests.test_context.HiveContextSQLTests) ... skipped "Unittest < 3.3 doesn't support mocking"
Skipped tests in pyspark.sql.tests.test_context with python2.7:
test_unbounded_frames (pyspark.sql.tests.test_context.HiveContextSQLTests) ... skipped "Unittest < 3.3 doesn't support mocking"
```
We don't have to use unittest 3.3 module to mock. And looks the test itself isn't compatible with Python 2.
This PR makes:
- Manually monkey-patch `sys.maxsize` to get rid of unittest 3.3 condition
- Use the built-in `reload` in Python 2, and `importlib.reload` in Python 3
## How was this patch tested?
Manually tested, and unit test is fixed.
Closes#23604 from HyukjinKwon/test-window.
Authored-by: Hyukjin Kwon <gurwls223@apache.org>
Signed-off-by: Bryan Cutler <cutlerb@gmail.com>
75d84498a4