Fix typo in error stack trace formatting for clearer output

[aboitreaud]

Fix a typo in error stack trace formatting by replacing "\\n" joins with traceback.format_exc(). The previous implementation used "\\n" to join lines, resulting in "\n" printed at the beginning of the lines. Fixing it by joining on "\n" would just add unnecessary line breaks and extra spacing in the stack trace. Since traceback functions already handle line breaks, this fix ensures proper formatting without redundant joins.

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[JDarDagran]

@kacpermuda could you please comment on that? I can see you made current join in #39813

[kacpermuda]

Hey @aboitreaud , thanks for the PR ! Apart from the problem you described with the formatting, you are not passing the exception object anymore to the formatting func. I'm thinking if there possibly is some edge case, where we the last exception raised is not the one that we have here in the adapter. Have you considered it here?

[uranusjr]

Does this change the error message? If so, can we include a comparison between old and new outputs in this PR?

[aboitreaud]

Hi @kacpermuda and @uranusjr and thanks for your comments!
Good catch, and thanks for pointing that out! I hadn’t fully considered the possibility of an edge case where the last exception raised might not be the one we have here in the adapter. To address this, I’m reverting back to using traceback.format_exception(error) instead of relying on traceback.format_exc(). This ensures we are handling the correct exception in all cases.

However, I don't think that joining on "\n" is necessary, here is of what the stack trace would look like:

• the old output, by joining on "\\n":

Traceback (most recent call last):
\n  File "example.py", line 6, in cause_error
    result = 1 / 0
\nZeroDivisionError: division by zero

• by joining on "\n":

Traceback (most recent call last):

  File "example.py", line 6, in cause_error
    result = 1 / 0

ZeroDivisionError: division by zero

• the new output, by joining on "":

Traceback (most recent call last):
  File "example.py", line 6, in cause_error
    result = 1 / 0
ZeroDivisionError: division by zero

[aboitreaud]

@uranusjr could I please also get your approval following Kacper's please ?

[aboitreaud]

👊 Gentle bump here @uranusjr @mobuchowski, could I get a code owner review please ?

[boring-cyborg]

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