Autoprofile fails if submodule contains a .py with with an invalid module name.

[Erotemic]

I saved a file "foo-v1.py" into a utils directory and that broke autoprofiling, as it recognized it as a Python file and tried to import it, but "foo-v1" is not a valid module name. A fix would be checking that the file has valid module name characters. We could also skip importing files that fail to import.

[TTsangSC]

Sorry for the radio silence on this issue, was busy with #391 last week and my vacation the week before.

Frankly I was caught by surprise, I'd have guessed that invalid module names should've been excluded by default. But it seems that both static analysis and pkgutil are all too happy to leave them be, and so we end up with stuff like

try:
    import mypkg.utils.foo-v1  # This is syntactically invalid
except ImportError:  # This normally handles failed imports
    ...
else:  # This handles the profiling of module contents upon successful import
    ...

in the module written by line_profiler.autoprofile.eager_preimports.write_eager_import_module().

I've since pushed a fix at #397.