I do not quite understand how that -m issue affects this. I always thought examples are run through sphinx gallery, which would os.chdir to the directory of the example file. In that case importing from the cwd should work fine, no?

Sorry my notes from last night were not super clear.

• The MakeFile we use invokes the build via

  matplotlib/doc/Makefile

  Line 6 in cff3da2

  SPHINXBUILD = python -msphinx

• previously when using -m the string '' was first in the path which means the cwd of the process is always in the path (even if you change directories)
• we, via sphinx-gallery, rely on this when we exec the example code to have the local imports work
• the fix in cpython to the security concern is that the 'cwd' is resolved as the directory you are launching from and that absolute path is put into sys.path. This in turn breaks our imports

ex

(dd36) ✔ /tmp 
13:05 $ python -m test_mod
3.6.6 | packaged by conda-forge | (default, Jul 26 2018, 09:53:17) 
[GCC 4.8.2 20140120 (Red Hat 4.8.2-15)]
['', '/home/tcaswell/mc3/envs/dd36/lib/python36.zip', '/home/tcaswell/mc3/envs/dd36/lib/python3.6']
(dd36) ✔ /tmp 
13:09 $ conda activate dd37
(dd37) ✔ /tmp 
13:09 $ python -m test_mod
3.7.0 | packaged by conda-forge | (default, Jul 23 2018, 21:39:36) 
[GCC 4.8.2 20140120 (Red Hat 4.8.2-15)]
['/tmp', '/home/tcaswell/mc3/envs/dd37/lib/python37.zip', '/home/tcaswell/mc3/envs/dd37/lib/python3.7']
(dd37) ✔ /tmp 
13:09 $ cat test_mod.py 
import sys
print(sys.version)
print(sys.path[:3])
(dd37) ✔ /tmp 

I think the fix is to in our sphinx conf add if '' not in sys.path: sys.path.append('') (or something to that effect) or to move this logic to sphinx gallery (and have it explicitly add / remove the cwd directory as it moves around the examples).

There is already a similar hack present in conf.py

so that might be the best option for now.

From a quick look at it, I'd suggest consolidating all unit examples that import basic_units into a single one together with basic_units itself; having each "this specific plotting method supports units" example in a separate file doesn't seem to be that helpful(?)