Try dropping jsonschema dependency (#59)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Steven Silvester <[email protected]>

jupyter_events/schema.py

@@ -4,7 +4,13 @@
 from typing import Type, Union
 
 from jsonschema import FormatChecker, validators
-from jsonschema.protocols import Validator
+
+try:
+    from jsonschema.protocols import Validator
+except ImportError:
+    from typing import Any
+
+    Validator = Any  # type:ignore
 
 from . import yaml
 from .validators import draft7_format_checker, validate_schema

pyproject.toml

@@ -23,10 +23,15 @@ classifiers = [
     "Programming Language :: Python :: 3",
 ]
 dependencies = [
-    "jsonschema[format-nongpl,format_nongpl]>=4.3.0",
+    "jsonschema[format-nongpl,format_nongpl]>=3.2.0,<4",
     "python-json-logger>=2.0.4",
     "pyyaml>=6.0",
     "traitlets>=5.3",
+    # The following are necessary to address an issue where pyproject.toml normalizes extra dependencies
+    # such that 'format_nongpl' is normalized to 'format-nongpl' which prevents these two validators from
+    # from being installed when jsonschema is <= 4.9 because jsonschema uses 'format_nongpl' in those releases.
+    "rfc3339-validator",
+    "rfc3986-validator>=0.1.1",
 ]
 dynamic = [
     "version",