tests failed on windows

[trim21]

there are some tests failed on windows:

test_multipart_encode_files_raises_exception_with_text_mode_file:

TemporaryFile on windows is binary mode.

httpx/tests/test_multipart.py

Lines 374 to 379 in 4b85e6c

	def test_multipart_encode_files_raises_exception_with_text_mode_file() -> None:
	url = "https://www.example.com"
	with tempfile.TemporaryFile(mode="w") as upload:
	files = {"file": ("test.txt", upload, "text/plain")}
	with pytest.raises(TypeError):
	httpx.Request("POST", url, data={}, files=files) # type: ignore

path seprator

httpx/tests/test_utils.py

Line 145 in 4b85e6c

def test_get_ssl_cert_file():

httpx/tests/test_utils.py

Line 125 in 4b85e6c

def test_logging_ssl(caplog):

not sure why...

httpx/tests/test_timeouts.py

Line 16 in 6d852d3

async def test_write_timeout(server):

also flaky tests:

httpx/tests/client/test_async_client.py

Line 21 in 4b85e6c

assert response.elapsed > timedelta(seconds=0)