Update dsc_job_runtime.py to fix error when extracting runtime.

Author: qiuosier

ads/jobs/builders/infrastructure/dsc_job_runtime.py

@@ -680,9 +680,13 @@ def _extract_envs(self, dsc_job) -> dict:
         """
         spec = super()._extract_envs(dsc_job)
         envs = spec.pop(PythonRuntime.CONST_ENV_VAR, {})
-        if self.__class__ == PythonRuntimeHandler and self.CONST_CODE_ENTRYPOINT not in envs:
+        if (
+            self.__class__ == PythonRuntimeHandler
+            and self.CONST_CODE_ENTRYPOINT not in envs
+        ):
             raise IncompatibleRuntime()
-        envs.pop(PythonRuntimeHandler.CONST_JOB_ENTRYPOINT)
+        # PyTorchDistributedRuntime does not require entrypoint.
+        envs.pop(PythonRuntimeHandler.CONST_JOB_ENTRYPOINT, None)
         spec.update(self._extract_specs(envs, self.SPEC_MAPPINGS))
         if PythonRuntime.CONST_PYTHON_PATH in spec:
             spec[PythonRuntime.CONST_PYTHON_PATH] = spec[