This fixes issues while reading some binaryfiles with auto precision detection, and also modernizes a few aspects of flopy.utils.binaryfile left-over from python2.

There are two changes to flopy.utils.binaryfile.binaryread():

1. Raises EOFError if attempting to read data beyond the end-of-file
2. Deprecate vartype=str, since bytes is the the return type with Python3

Other refactors:

• Simplify conventional ASCII range checks by converting bytes to a list of int, then check if bytes are within range
• Remove checks if bytes are not str, and use .encode("ascii") where appropriate

Examples of issues

CellBudgetFile

Reading a cell budget file that contains imeth=5 with precision="auto" (the default):

python -c "from flopy.utils import *; print(CellBudgetFile('examples/data/preserve_unitnums/testsfr2.ghb.cbc').headers)"

previously this will hang indefinitely since it is attempting to read data at the end of the file without raising any exception. This example is fixed with this PR.

HeadFile

And this is not so much a fix, but a less confusing error:

python -c "from flopy.utils import *; HeadFile('examples/data/mf6/create_tests/test_transport/expected_output/gwt_mst03.ucn')"

the exception is changed from:

IndexError: index 0 is out of bounds for axis 0 with size 0

to:

EOFError

I have some pending changes to resolve this issue, due after this one.