Failing of alll database metrics.

[harshad16]

Describe the bug
All graph metrics are failing due to connection errors.

{"name": "thoth.metrics_exporter", "levelname": "ERROR", "module": "wsgi", "lineno": 89, "funcname": "func_wrapper", "created": 1615921004.0016477, "asctime": "2021-03-16 18:56:44,001", "msecs": 1.6477108001708984, "relative_created": 4819.690942764282, "process": 23, "message": "Failed to run metrics gathering job DBMetrics.set_script_head_revision\nTraceback (most recent call last):\n  File \"/opt/app-root/src/thoth/metrics_exporter/jobs/base.py\", line 91, in graph\n    cls._GRAPH.connect()\n  File \"/opt/app-root/lib64/python3.8/site-packages/thoth/storages/graph/postgres.py\", line 299, in connect\n    if not database_exists(self._engine.url):\n  File \"/opt/app-root/lib64/python3.8/site-packages/thoth/storages/graph/postgres_utils.py\", line 79, in database_exists\n    database, url.database = url.database, os.getenv('KNOWLEDGE_GRAPH_DATABASE')\nAttributeError: can't set attribute\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n  File \"/opt/app-root/src/wsgi.py\", line 87, in func_wrapper\n    job()\n  File \"<decorator-gen-10>\", line 2, in set_script_head_revision\n  File \"/opt/app-root/src/thoth/metrics_exporter/jobs/base.py\", line 42, in register_metric_job\n    method(*args, **kwargs)\n  File \"/opt/app-root/src/thoth/metrics_exporter/jobs/db.py\", line 124, in set_script_head_revision\n    \"metrics-exporter\", cls.graph().get_script_alembic_version_head(), Configuration.DEPLOYMENT_NAME\n  File \"/opt/app-root/src/thoth/metrics_exporter/jobs/base.py\", line 94, in graph\n    raise Exception(\"Raise a flag if there is an error connecting to database. %r\", e)\nException: ('Raise a flag if there is an error connecting to database. %r', AttributeError(\"can't set attribute\"))"}

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/app-root/lib64/python3.8/site-packages/thoth/storages/graph/postgres.py", line 299, in connect
    if not database_exists(self._engine.url):
  File "/opt/app-root/lib64/python3.8/site-packages/thoth/storages/graph/postgres_utils.py", line 79, in database_exists
    database, url.database = url.database, os.getenv('KNOWLEDGE_GRAPH_DATABASE')
AttributeError: can't set attribute

[harshad16]

fixed by the v0.14.1
this was caused by the issue of sqlalchemy.
pinning it has fixed this.