/test_examples creates AttributeError and AssertionError while running pytest

[miriabeh]

commands used up until the Errors:
1. sudo apt-get install libgl1-mesa-glx libegl1-mesa libxrandr2 libxrandr2 libxss1 libxcursor1 libxcomposite1 libasound2 libxi6 libxtst6
2. bash ~/Downloads/Anaconda3-2024.06-1-Linux-x86_64.sh
3. source anaconda3/bin/activate
4. conda init
5. cd git_repos/oemof-tabular/
6. conda create –name oemof-tabular ‚python=3.9‘
7. conda activate oemof-tabular
8. pip install oemof.tabular
9. pip install pytest
10. pytest .
11. Pip install ‚numpy<2.0.0‘
12. pytest .
13. conda install conda-forge::coin-or-cbc
14. pytest .

10 and 11 is related to #178
13 is due to an ApplicationError: No executable found for solver 'cbc'

Error Messages:

• FAILED tests/test_examples.py::test_example_datapackage_readability - AttributeError: If fix is set in a flow (except InvestmentFlow), nominal_value must be set as well.
• FAILED tests/test_examples.py::test_scripting_examples - AttributeError: module 'oemof.tabular.tools.postprocessing' has no attribute 'bus_results'
• FAILED tests/test_examples.py::test_examples_datapackages_scripts_infer - AssertionError: Failed matching json_file_1 with json_file_2: