warp silently fails on an exclusive solidity version interval

[temyurchenko]

How to reproduce:

In the example contract ERC20.sol replace the first line with pragma solidity >0.4.18;.

Expected

Warp successfully generates an ERC20.cairo file.

Actual

There is no ERC20.cairo file and no indication of failure or reasons for failure

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I think the issue is that get_source_version in Compile.py simply grabs the first version boundary without considering that it might be an exclusive boundary as in the example above. Thus, compiling the contract with this version fails (for some reason, silently)