Remove imp package to prevent Warning deprecation message

[ipeluffo]

Remove imp package to prevent getting deprecation warning message.

When importing venusian, it imports imp which reports some deprecation warning messages:

venusian/__init__.py:1: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
    import imp

[digitalresistor]

Where are these magic numbers documented?

[ipeluffo]

@bertjwregeer , I took the values from the imp source code:
https://github.com/python/cpython/blob/master/Lib/imp.py#L35-L45

Having said that, in this case I think they could be any value.

[fschulze]

I don't think these should be hard coded. According to https://docs.python.org/3/library/imp.html?highlight=imp#imp.get_magic the value may be different for each Python version. It also says which value to use from importlib instead: https://docs.python.org/3/library/importlib.html#module-importlib.machinery I haven't figured out the full mapping yet.

[digitalresistor]

If we go Python 3 only, we can ignore the whole "source file" vs ".pyc" file issue entirely, because .pyc files are not stored in the same path as source files, and we would potentially want to import .pyc files.

[ipeluffo]

Any update on this? Thanks