René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"setup downloads sometimes fails CERTIFICATE_VERIFY_FAILED","articleBody":"\u003c!--To help us understand and resolve your issue, please fill out the form to the best of your ability.--\u003e\r\n\u003c!--You can feel free to delete the sections that do not apply.--\u003e\r\n\r\n### Bug report\r\n\r\nSometimes (depending on how Python has been installed) one might see a \r\n```bash\r\n\u003curlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1056)\u003e\r\n```\r\nerror.\r\n\r\n**Fix**\r\n\r\nThe easy fix is to ensure `certifi` certificates path is added to the `urlopen` method.\r\n\r\nI.e. in your `setupext.py` you may need:\r\n```python\r\nimport certifi\r\n    with urlopen(\r\n            Request(url, headers={\"User-Agent\": \"\"}), cafile=certifi.where()) as req:\r\n        file_contents = BytesIO(req.read())\r\n```\r\n\r\nProbably there needs to be some try-execpt-(import certifi-fix) to handle this.\r\n\r\n**Matplotlib version**\r\n\r\nThis happens when `setup.py` tries to download files, e.g. the recent change to jquery download. So basically I have only seen this in 2.2.4 and 3.0.3.\r\n\r\nAgreed, this may be because my installation is not the same as system installations, but it may happen elsewhere I guess.\r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\n\r\n","author":{"url":"https://github.com/zerothi","@type":"Person","name":"zerothi"},"datePublished":"2019-05-08T12:01:11.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/14169/matplotlib/issues/14169"}