Fix for python 3.12 compatibility

pyproject.toml

@@ -14,7 +14,7 @@ requires = [
     "lxml >= 4.8",
     "pandas >= 1.3",
     "pydantic >=1.9.2, < 2.0"]
-requires-python = ">=3.9.6,<3.12"
+requires-python = ">=3.9.6"
 keywords = "statistics, SDMX, pandas, data, economics, science"
 classifiers = [
 "Intended Audience :: Developers",
@@ -29,17 +29,20 @@ classifiers = [
     "Topic :: Scientific/Engineering :: Information Analysis",
 "License :: OSI Approved :: Apache Software License"]
 
-[tool.flit.metadata.requires-extra]  
+[tool.flit.metadata.requires-extra]
 cache = ["requests_cache >= 0.9.5"]
 schema = ["appdirs >= 1.4"]
-doc = ["sphinx >= 5.2", 
+doc = ["sphinx >= 5.2",
 "IPython >= 7.20"]
-test = ["pytest >= 5", 
-"requests-mock >= 1.4"]
+test = [
+    "pytest >= 5",
+    "requests-mock >= 1.4",
+    "pytest-cov >= 5"
+]
 
 [tool.flit.metadata.urls]
     Homepage = "https://pandasdmx.readthedocs.io/en/latest/"
 
 [tool.flit.sdist]
 include = ["LICENSE", 'README.rst']
-exclude = ['pandasdmx/tests']
+exclude = ['pandasdmx/tests']