Cannot create Contract from etherscan contracts verified via JSON input

[iamdefinitelyahuman]

What was wrong?

Contract.from_explorer fails when the source code is verified using the standard JSON input.

As an example: 0xaf1610D242c7CdD30c546844aF75c147C12e94F9

>>> Contract.from_explorer("0xaf1610D242c7CdD30c546844aF75c147C12e94F9") 
  File "<console>", line 1, in <module>
  File "eth_brownie-1.8.2-py3.8.egg/brownie/network/contract.py", line 440, in __init__
    contract = self.from_explorer(address, owner=owner, silent=True)
  File "eth_brownie-1.8.2-py3.8.egg/brownie/network/contract.py", line 651, in from_explorer
    build = compile_and_format(
  File "eth_brownie-1.8.2-py3.8.egg/brownie/project/compiler/__init__.py", line 132, in compile_and_format
    output_json = compile_from_input_json(input_json, silent, allow_paths)
  File "eth_brownie-1.8.2-py3.8.egg/brownie/project/compiler/__init__.py", line 247, in compile_from_input_json
    return solidity.compile_from_input_json(input_json, silent, allow_paths)
  File "eth_brownie-1.8.2-py3.8.egg/brownie/project/compiler/solidity.py", line 72, in compile_from_input_json
    raise CompilerError(e)
CompilerError: Compiler returned the following errors:

Pool-flattened.sol:1:1: ParserError: Expected pragma, import directive or contract/interface/library definition.
{{

How can it be fixed?

In Contract.from_explorer, check the format of SourceCode returned from Etherscan and handle accordingly.

[iamdefinitelyahuman]

This issue is now causing the test suite to fail - it should be handled ASAP