Show cause of the error when fixture can't not be loaded

[eduardor2k]

When a fixture can't be loaded, you only get a generic error telling you which fixture can't be loaded, it would be more helpful if in that message we get the cause of the error

1) Unit\RequestApiTest::testCreate CException: Exception loading row req1 in fixture /var/www/html/test/yiitools/protected/tests/fixtures/requests.php

to

1) Unit\RequestApiTest::testCreate CException: Exception loading row req1 in fixture /var/www/html/test/yiitools/protected/tests/fixtures/requests.php Error: CDbCommand failed to execute the SQL statement: SQLSTATE[22007]: Invalid datetime format: 1292 Incorrect datetime value: '1691576897' for column 'date_added' at row 1

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Tests pass?	✔️
Fixed issues	comma-separated list of tickets # fixed by the PR, if any

[what-the-diff]

PR Summary

• Improved error messaging in the database fixture manager file
  The adjustment in the file CDbFixtureManager.php enhances the clarity of error messages experienced during its operation. Now, the specific error message from the system exception will be included, providing more detail for troubleshooting. This is crucial for speeding up problem identification and rectification.

[marcovtwout]

The original exception message is not lost (passed as 3rd argument to CException) but it might depend on the environment or error handler if you get to see the full stack trace containing that error.

The change looks helpful though and I see no BC issues. Could you add a line to the CHANGELOG as well?

[eduardor2k]

Yes, no problem!

[eduardor2k]

@marcovtwout done! Let me know if you need anything!

[marcovtwout]

Merged, thanks!