René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Warning treated as error while generating docs","articleBody":"### Bug report\r\n\r\n**Bug summary**\r\n\r\nI get the following `WARNING` while generating docs.\r\n\r\n```\r\nWarning, treated as error:\r\n/home/aashil/github/matplotlib/doc/api/_as_gen/matplotlib.axes.Axes.clabel.rst:83: WARNING: Exception occurred in plotting contour_demo\r\n from /home/aashil/github/matplotlib/doc/mpl_examples/pylab_examples/contour_demo.py:\r\nTraceback (most recent call last):\r\n  File \"/usr/local/lib/python2.7/dist-packages/matplotlib-2.0.0+3486.g8c57dae-py2.7-linux-x86_64.egg/matplotlib/sphinxext/plot_directive.py\", line 525, in run_code\r\n    six.exec_(code, ns)\r\n  File \"/usr/local/lib/python2.7/dist-packages/six.py\", line 699, in exec_\r\n    exec(\"\"\"exec _code_ in _globs_, _locs_\"\"\")\r\n  File \"\u003cstring\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"\u003cstring\u003e\", line 55, in \u003cmodule\u003e\r\n  File \"/usr/local/lib/python2.7/dist-packages/matplotlib-2.0.0+3486.g8c57dae-py2.7-linux-x86_64.egg/matplotlib/__init__.py\", line 916, in __setitem__\r\n    raise ValueError(\"Key %s: %s\" % (key, str(ve)))\r\nValueError: Key contour.negative_linestyle: linestyle must be a string or an even-length sequence of floats.\r\n\r\nBuilding HTML failed.\r\n```\r\nThe command from `contour_demo.py` which throws the warning is:\r\n```\r\nCS = plt.contour(Z, levels,\r\n                 origin='lower',\r\n                 linewidths=2,\r\n                 extent=(-3, 3, -2, 2))\r\n```\r\n\r\nI think it's expecting positive values for extent.\r\n\r\n\r\n**Code for reproduction**\r\n\r\n- A minimum code snippet required to reproduce the bug, also minimizing the number of dependencies required\r\n\r\n```python\r\npython make.py html\r\n```\r\n**Matplotlib version**\r\n\r\n- Matplotlib version 2.0.0+3486.g8c57dae, Python version 2.7.12 and Platform (Ubuntu 16.04)\r\n- I built Matplotlib from sources and python came pre-installed with Ubuntu 16.04\r\n\r\n","author":{"url":"https://github.com/aashil","@type":"Person","name":"aashil"},"datePublished":"2017-02-25T04:27:21.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":9},"url":"https://github.com/8145/matplotlib/issues/8145"}