import_csv: catch too many columns error

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.06% :tada:

Comparison is base (73b4c53) 95.72% compared to head (675cad5) 95.79%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #207 +/- ## ========================================== + Coverage 95.72% 95.79% +0.06% ========================================== Files 42 42 Lines 2711 2708 -3 Branches 338 339 +1 ========================================== - Hits 2595 2594 -1 + Misses 92 90 -2 Partials 24 24 ``` | [Files Changed](https://app.codecov.io/gh/BEMServer/bemserver-core/pull/207?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BEMServer) | Coverage Δ | | |---|---|---| | [bemserver\_core/input\_output/timeseries\_data\_io.py](https://app.codecov.io/gh/BEMServer/bemserver-core/pull/207?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BEMServer#diff-YmVtc2VydmVyX2NvcmUvaW5wdXRfb3V0cHV0L3RpbWVzZXJpZXNfZGF0YV9pby5weQ==) | `99.14% <100.00%> (+0.83%)` | :arrow_up: |

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