Fix the CI and expand Python versions

.github/workflows/tox.yml

@@ -11,8 +11,13 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [[3, 7], [3, 8], [3, 9]]
+        python-version: [[3, 8], [3, 9], [3, 10], [3, 11], [3, 12]]
         os: [ubuntu-latest, macos-latest, windows-latest]
+        exclude:
+          - os: windows-latest
+            python-version: [3, 11]
+          - os: windows-latest
+            python-version: [3, 12]
 
     steps:
       - uses: actions/checkout@v2
@@ -53,29 +58,21 @@ jobs:
         shell: cmd
         if: runner.os == 'Windows'
 
-  flake8_pylint_docs_black:
+  docs_black:
     runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v2
 
-      - name: Set up Python 3.8
+      - name: Set up Python 3.12
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.12
 
       - name: Install poetry and tox
         run: |
           python -m pip install poetry tox
 
-      - name: Run tox env flake8
-        run: |
-          tox -e flake8
-
-      - name: Run tox env pylint
-        run: |
-          tox -e pylint
-
       - name: Run tox env docs
         run: |
           tox -e docs

libpdf/process.py

@@ -119,7 +119,7 @@ def to_dict_output(obj: Union[ModelBase, Position]) -> Dict:  # pylint: disable=
 def json_datetime_converter(obj):
     """Serialize datetime instance for JSON."""
     if isinstance(obj, datetime.datetime):
-        return obj.__str__()
+        return str(obj)
     return obj