Bug summary

The function _copy_css_file in sphinxext/plot_directive.py assumes that the _static directory already exists. If it doesn't, then rather than creating _static/plot_directive.css with the appropriate content, it instead writes that content to a file _static. If another part of Sphinx then tries to create a directory _static, it results in an error.

We run into this problem in Sagemath (see https://trac.sagemath.org/ticket/32262) because we have a complicated directory layout for Sphinx output, and the _static directory may not be created right away.

Code for reproduction

Build Sagemath + the latest matplotlib (https://trac.sagemath.org/ticket/31580).

Actual outcome

Sphinx raises an error: OSError: WARNING: cannot copy static file FileExistsError(17, 'File exists'). A more complete traceback is at https://trac.sagemath.org/ticket/31580.

Expected outcome

Used to work with version 3.3.4 of matplotlib, which I believe is before the function _copy_css_file was introduced.

Operating system

Observed on OS X and linux

Matplotlib Version

3.4.2

Matplotlib Backend

No response

Python version

3.9

Jupyter version

No response

Other libraries

No response

Installation

No response

Conda channel

No response