feat: mock strategy for rescue use[StrategyGUSDRescue] (yearn#78)

* feat: mock strategy for rescue use[StrategyGUSDRescue]
* fix: style fixes
* fix: mock withdrawAll()
* fix: small linter change

Co-authored-by: dmolina79 <[email protected]>

contracts/strategies/StrategyGUSDRescue.sol

@@ -0,0 +1,48 @@
+pragma solidity ^0.5.17;
+
+interface IERC20 {
+    function totalSupply() external view returns (uint256);
+
+    function balanceOf(address account) external view returns (uint256);
+
+    function transfer(address recipient, uint256 amount) external returns (bool);
+
+    function allowance(address owner, address spender) external view returns (uint256);
+
+    function decimals() external view returns (uint256);
+
+    function approve(address spender, uint256 amount) external returns (bool);
+
+    function transferFrom(
+        address sender,
+        address recipient,
+        uint256 amount
+    ) external returns (bool);
+
+    event Transfer(address indexed from, address indexed to, uint256 value);
+    event Approval(address indexed owner, address indexed spender, uint256 value);
+}
+
+contract StrategyGUSDRescue {
+    address public constant want = address(0x056Fd409E1d7A124BD7017459dFEa2F387b6d5Cd);
+    address public governance = address(0xFEB4acf3df3cDEA7399794D0869ef76A6EfAff52);
+
+    constructor() public {}
+
+    function getName() external pure returns (string memory) {
+        return "StrategyGUSDRescue";
+    }
+
+    function deposit() public {
+        uint256 _want = IERC20(want).balanceOf(address(this));
+        IERC20(want).transfer(governance, _want);
+    }
+
+    function withdrawAll() public returns (uint256) {
+        return 0;
+    }
+
+    function balanceOf() public pure returns (uint256) {
+        return 0;
+    }
+}