More control over stderr in stdio client

[sesajad]

Description

Currently, a TextIO object (defaulting to sys.stderr) must be set for errlog when creating a new stdio client session.

python-sdk/src/mcp/client/stdio/__init__.py

Line 106 in 2aa1ad2

async def stdio_client(server: StdioServerParameters, errlog: TextIO = sys.stderr):

However, the underlying calls to Python's native Popen and anyio.create_process both support subprocess.DEVNULL: int = -3 for stderr, which allows the stream to be ignored.
By updating the type hint, we can easily support int for errlog. This change would benefit downstream projects and resolve issues for CLI users. Furthermore, I believe ignoring errlog is a better default than piping them into stderr, as the current behaviour can create unexpected side-effects that are difficult to trace.

References

Related Issues:
#156
langchain-ai/langchain-mcp-adapters#72

Documentation:
https://docs.python.org/3/library/subprocess.html#subprocess.Popen
https://anyio.readthedocs.io/en/stable/api.html#anyio.open_process