Python: Throw exception on image error

[emmanuel-ferdman]

Motivation and Context

Description

This small PR throws the forgotten exception on image error.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
agents/open_ai
responses_agent_thread_actions.py	341	107	68%	167, 184, 195, 206–207, 374–376, 390, 395, 402, 420–421, 425, 469–471, 474, 492–493, 502–504, 508, 512–513, 517–519, 530–532, 554, 556–557, 564–565, 567–568, 570, 572–573, 575–576, 659–661, 673–674, 676–680, 682–688, 690–699, 701–702, 706–709, 716–718, 723, 725, 786–789, 830–831, 835–837, 839, 864–865, 867–871, 873, 883–884, 892, 896, 903, 909, 973
TOTAL	27106	4623	82%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3624	22 💤	0 ❌	0 🔥	1m 55s ⏱️