Fix several jsonschema DeprecationWarning (#1128)

* address DeprecationWarnings from jsonschema

* use `referencing` for Python >= 3.8

* undo unrelated change by auto linter

clearml/backend_api/session/request.py

@@ -1,7 +1,14 @@
 import abc
 
-import jsonschema
 import six
+from jsonschema.exceptions import FormatError, SchemaError, ValidationError
+
+try:
+    # Since `referencing`` only supports Python >= 3.8, this try-except blocks maintain support
+    # for earlier python versions.
+    from referencing.exceptions import Unresolvable
+except ImportError:
+    from jsonschema.exceptions import RefResolutionError as Unresolvable
 
 from .apimodel import ApiModel
 from .datamodel import DataModel
@@ -39,8 +46,7 @@ class BatchRequest(Request):
 
     _batched_request_cls = abc.abstractproperty()
 
-    _schema_errors = (jsonschema.SchemaError, jsonschema.ValidationError, jsonschema.FormatError,
-                      jsonschema.RefResolutionError)
+    _schema_errors = (SchemaError, ValidationError, FormatError, Unresolvable)
 
     def __init__(self, requests, validate_requests=False, allow_raw_requests=True, **kwargs):
         super(BatchRequest, self).__init__(**kwargs)
@@ -70,8 +76,7 @@ class BatchRequest(Request):
         for i, req in enumerate(self.requests):
             try:
                 req.validate()
-            except (jsonschema.SchemaError, jsonschema.ValidationError,
-                    jsonschema.FormatError, jsonschema.RefResolutionError) as e:
+            except (SchemaError, ValidationError, FormatError, Unresolvable) as e:
                 raise Exception('Validation error in batch item #%d: %s' % (i, str(e)))
 
     def get_json(self):

requirements.txt

@@ -14,6 +14,7 @@ python-dateutil>=2.6.1
 pyjwt>=2.4.0,<2.9.0 ; python_version > '3.5'
 pyjwt>=1.6.4,<2.0.0 ; python_version <= '3.5'
 PyYAML>=3.12
+referencing<0.40 ; python_version >= '3.8'
 requests>=2.20.0
 six>=1.13.0
 typing>=3.6.4 ; python_version < '3.5'