SciTools
Replace urllib.request with urllib3 to support WebAssembly
As discussed in #2514, urllib.request is not supported in WebAssembly. This replaces urllib.request where needed with urllib3 which does work with WebAssembly. I've tried to keep the code changes to a minimum and to reuse existing semantic patterns.
The linter did introduce new lines in one of the imports. I found it odd but left it in place.
Rationale
This enables the use of Cartopy is Pyodide and JupyterLite. Without it, downloading of shape files, etc., fail. See #2514.
Implications
I've run the unit tests and nothing new fails. It's also been tested in JupyterLite and works. There is a chance that the download code path hasn't been fully tested and something may still need to be changed to support urllib3.
This also introduces a new dependency, even though urllib3 is widely available. It is also an existing package in Pyodide.
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Is this PR still active? I am running into the same problem and would love to see a solution.
It is still open, but needs a champion that is interested in merging it in. I'm not in favor of it because it adds a new dependency that seems somewhat unncessary except for a WASM environment, but I won't block if someone else thinks this is the way to go.
See the comment here and the thread for workarounds/suggestions on how to approach this: https://github.com/SciTools/cartopy/issues/2514#issuecomment-2763101149
The workaround is reasonably easy and works for me. Thanks for pointing to it.
On the other hand, "except for a WASM environment" seems like a very good reason to me. Especially considering that WASM is a pretty universal standard these days rapidly gaining popularity through platforms such as JupyterLite. But I'm not neutral.
