urllib.error.URLError when running svg2png on SVGs containing internal xlink:hrefs

Hello, I've found other references (https://github.com/Kozea/CairoSVG/issues/134) to this issue, but I'm still having trouble processing SVGs containing internal xlink:hrefs with CairoSVG 2.4.0.

Here's a general idea of my SVG structure:
```

```

I'm calling CairoSVG from a python script with this code:
`cairosvg.svg2png(url='svgs/' + svgName, write_to='svgs/png.png', scale=2)`

When I run my code on SVGs that don't contain internal hrefs everything processes as expected, but when I try to run my code on an SVG with internal hrefs I receive the following error:
`urllib.error.URLError: `

How can I fix this behavior so CairoSVG will properly parse internal hrefs?

Reproduce the issue with the provided SVG and the cairosvg.svg2png(url=..., write_to=..., scale=2) entry point. Trace how the internal xlink:href value #arrows is resolved on Windows, especially the conversion to a file URL. Done means SVGs with internal hrefs render successfully without attempting to open a %23arrows file.

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