[PLT-1359] Vb/labeling service improve message reporting plt 1359

[vbrodsky]

Description

Story: https://labelbox.atlassian.net/browse/PLT-1359

Improvements to error reporting for labeling service request()

Before:

labelbox.exceptions.LabelboxError:  [{"errorType":"DATA_STEP","errorMessage":"Data is missing"},{"errorType":"ONTOLOGY_INSTRUCTIONS","errorMessage":"Ontology instructions are not completed"}], None"

After:

labelbox.exceptions.LabelboxError: Data is missing. Ontology instructions are not completed('Data is missing. Ontology instructions are not completed')

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Document change (fix typo or modifying any markdown files, code comments or anything in the examples folder only)

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Changes to Core Features

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