assertion with multi-line string needlessly spans multiple lines

[Aran-Fey]

Describe the bug

When an assert statement has a multi-line string, the condition is split across 3 lines for no reason.

To Reproduce

For example, take this code:

assert some_var == expected_result, f"""
expected: {expected_result}
actual: {some_var}"""

And run it with these arguments:

$ black file.py

The resulting output is:

assert (
    some_var == expected_result
), f"""
expected: {expected_result}
actual: {some_var}"""

Expected behavior

The condition should remain as a single line.

Environment

• Black's version: @ed770b
• OS and Python version: Whatever https://black.vercel.app uses

[Drachenfels]

Would not be marginally cleaner to re-format it to:

assert (
    some_var == expected_result,
    f"""expected: {expected_result}
    actual: {some_var}"""
)

[JelleZijlstra]

Would not be marginally cleaner to re-format it to:

assert (
    some_var == expected_result,
    f"""expected: {expected_result}
    actual: {some_var}"""
)

No, because that would change the meaning of the code (and make the assertion useless).