JOSS review: Fix linter failures

[rmsare]

A final side note: I believe that a linter such as flake8 should be used in order to prevent bugs and conform to Python standards. From the root of the repository (commit d97450d), the call to flake8 returned the following (note that line ./pymccrgb/pointutils.py:28 of crop_to_polygon would raise a NameError):

./setup.py:11:80: E501 line too long (92 > 79 characters)
./setup.py:38:80: E501 line too long (80 > 79 characters)
./docs/source/conf.py:58:1: E302 expected 2 blank lines, found 1
./docs/source/conf.py:86:1: E402 module level import not at top of file
./docs/source/conf.py:87:1: E402 module level import not at top of file
./docs/source/conf.py:156:1: E402 module level import not at top of file
./pymccrgb/core.py:90:1: W293 blank line contains whitespace
./pymccrgb/core.py:94:1: W293 blank line contains whitespace
./pymccrgb/core.py:103:1: W293 blank line contains whitespace
./pymccrgb/core.py:205:72: W291 trailing whitespace
./pymccrgb/core.py:211:22: W291 trailing whitespace
./pymccrgb/core.py:222:1: W293 blank line contains whitespace
./pymccrgb/core.py:318:80: E501 line too long (87 > 79 characters)
./pymccrgb/core.py:339:80: E501 line too long (83 > 79 characters)
./pymccrgb/__init__.py:1:1: F401 '.core' imported but unused
./pymccrgb/__init__.py:1:1: F401 '.datasets' imported but unused
./pymccrgb/__init__.py:1:1: F401 '.features' imported but unused
./pymccrgb/__init__.py:1:1: F401 '.ioutils' imported but unused
./pymccrgb/__init__.py:1:1: F401 '.pointutils' imported but unused
./pymccrgb/__init__.py:1:1: F401 '.plotting' imported but unused
./pymccrgb/__init__.py:2:1: F401 '.core.mcc' imported but unused
./pymccrgb/__init__.py:2:1: F401 '.core.mcc_rgb' imported but unused
./pymccrgb/__init__.py:3:1: F401 '.ioutils.read_data' imported but unused
./pymccrgb/__init__.py:3:31: W291 trailing whitespace
./pymccrgb/ioutils.py:10:15: E225 missing whitespace around operator
./pymccrgb/ioutils.py:12:1: E302 expected 2 blank lines, found 1
./pymccrgb/ioutils.py:39:80: E501 line too long (80 > 79 characters)
./pymccrgb/ioutils.py:43:80: E501 line too long (80 > 79 characters)
./pymccrgb/ioutils.py:46:80: E501 line too long (100 > 79 characters)
./pymccrgb/ioutils.py:51:80: E501 line too long (81 > 79 characters)
./pymccrgb/ioutils.py:63:22: W291 trailing whitespace
./pymccrgb/ioutils.py:129:5: F841 local variable 'count' is assigned to but never used
./pymccrgb/ioutils.py:159:80: E501 line too long (117 > 79 characters)
./pymccrgb/ioutils.py:160:9: E131 continuation line unaligned for hanging indent
./pymccrgb/ioutils.py:170:5: F841 local variable 'count' is assigned to but never used
./pymccrgb/ioutils.py:183:80: E501 line too long (88 > 79 characters)
./pymccrgb/ioutils.py:184:9: E131 continuation line unaligned for hanging indent
./pymccrgb/ioutils.py:192:5: F841 local variable 'count' is assigned to but never used
./pymccrgb/pointutils.py:5:1: F401 'pdal' imported but unused
./pymccrgb/pointutils.py:28:27: F821 undefined name 'poly'
./pymccrgb/pointutils.py:78:1: W293 blank line contains whitespace
./pymccrgb/pointutils.py:90:80: E501 line too long (111 > 79 characters)
./pymccrgb/pointutils.py:113:80: E501 line too long (104 > 79 characters)
./pymccrgb/pointutils.py:149:80: E501 line too long (99 > 79 characters)
./pymccrgb/classification.py:36:22: W291 trailing whitespace
./pymccrgb/classification.py:50:80: E501 line too long (88 > 79 characters)
./pymccrgb/colorize.py:3:1: F401 'pdal' imported but unused
./pymccrgb/plotting.py:10:1: F401 'mpl_toolkits.mplot3d.Axes3D' imported but unused
./pymccrgb/plotting.py:75:80: E501 line too long (83 > 79 characters)
./pymccrgb/plotting.py:110:80: E501 line too long (80 > 79 characters)
./pymccrgb/plotting.py:189:80: E501 line too long (83 > 79 characters)
./pymccrgb/plotting.py:196:80: E501 line too long (81 > 79 characters)
./pymccrgb/plotting.py:202:12: F821 undefined name 'updated'
./pymccrgb/plotting.py:205:5: F841 local variable 'ymax' is assigned to but never used
./pymccrgb/plotting.py:207:80: E501 line too long (81 > 79 characters)
./pymccrgb/datasets.py:46:80: E501 line too long (92 > 79 characters)
./pymccrgb/tests/test_features.py:5:1: F401 'pytest' imported but unused
./pymccrgb/tests/test_features.py:29:80: E501 line too long (80 > 79 characters)
./pymccrgb/tests/test_features.py:44:80: E501 line too long (83 > 79 characters)
./pymccrgb/tests/test_features.py:51:80: E501 line too long (81 > 79 characters)
./pymccrgb/tests/context.py:4:80: E501 line too long (85 > 79 characters)
./pymccrgb/tests/context.py:6:1: E402 module level import not at top of file
./pymccrgb/tests/context.py:6:1: F401 'pymccrgb' imported but unused
./pymccrgb/tests/test_core.py:5:1: F401 'pytest' imported but unused
./pymccrgb/tests/test_core.py:29:80: E501 line too long (83 > 79 characters)
./pymccrgb/tests/test_core.py:35:80: E501 line too long (99 > 79 characters)
./pymccrgb/tests/test_core.py:94:80: E501 line too long (87 > 79 characters)

openjournals/joss-reviews#1777

[rmsare]

I've fixed the linter failures in the main codebase. I left tests and docs alone.

• Formatting uses black with a line length of 88 chars. I added this to CI.
• I chose to keep a couple of long lines where formatted strings are printed
• flake8 flags some of my convenience imports, like those in init.py and Axes3D. They are used, so I didn't change these.