I had an issue where pandas would report an import error, upon attempting to use a buffer from io's StringIO class, during the use of read_csv() from pandas.
Installing fsspec (an optional package for pandas) alone is not enough for pandas to be able to import fsspec. The dependecies for fsspec need also be installed, I don't know why the maintainers are not handling this with install.py, but here we are. I'll send them a message, but if you find your self in this condition, try:
pip install tox tox-conda