OpenZeppelin unit test fails. Error: invalid literal for int() with base 16: ''

[mich-master]

Impact:
Proxy + Neon EVM <-> OpenZeppelin library compatibility
Safe math operations computation

STR:

1. Set up Truffle environment for the OpenZeppelin library as described
   Other changes neonlabsorg/neon-evm#219
2. Run the unit test for "SafeMath" contract
   truffle --network solana test ./test/utils/math/SafeMath.test.js

Actual result:
Error message

Contract: SafeMath
with default revert message
add
reverts on addition overflow:
Wrong kind of exception received
+ expected - actual
-invalid literal for int() with base 16: ''
+revert

Expected result:
Test passed successfully.

Additional info:
OpenZeppelin test: Contract: ERC20FlashMint flashLoan.more than maxFlashLoan

    it ('more than maxFlashLoan', async function () {
      const receiver = await ERC3156FlashBorrowerMock.new(true, true);
      const data = this.token.contract.methods.transfer(other, 10).encodeABI();
      // _mint overflow reverts using a panic code. No reason string.
      await expectRevert.unspecified(this.token.flashLoan(receiver.address, this.token.address, MAX_UINT256, data));
    });

The revert result can be returned through different solidity ways. In any case, the first 4 bytes contain a selector, which identifies the method used to encode the result. Some possible values:

• 08c379a0 - Error(string)
• 4e487b71 - Panic(uint256)

We should analyze the selector before parse followed data:
https://github.com/neonlabsorg/proxy-model.py/blob/5cb42d5e7f951338e787f669e96512499b081a89/proxy/plugin/solana_rest_api_tools.py#L363-L371

See also:

• https://github.com/ethereum/EIPs/blob/master/EIPS/eip-140.md
• Panic error codes are hard to use ethereum/solidity#10432
• EIP 838: ABI specification for REVERT reason string ethereum/EIPs#838

[mich-master]

The error message "invalid literal for int() with base 16: ''" seems to be from Python.
Probably, the bug is located in Proxy.