Extract old OpenZeppelin code to avoid conflicts

contracts/PrivatePoolNFT.sol

@@ -25,8 +25,8 @@ import "@boringcrypto/boring-solidity/contracts/interfaces/IMasterContract.sol";
 import "@boringcrypto/boring-solidity/contracts/libraries/BoringRebase.sol";
 import "@boringcrypto/boring-solidity/contracts/libraries/BoringERC20.sol";
 import "@sushiswap/bentobox-sdk/contracts/IBentoBoxV1.sol";
-import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
-import "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
+import "./interfaces/IERC721.sol";
+import "./interfaces/IERC721Receiver.sol";
 
 /// @title PrivatePoolNFT
 /// @dev This contract allows contract calls to any contract (except BentoBox)

contracts/interfaces/IERC165.sol

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: MIT
+// Taken from OpenZeppelin contracts v3
+
+pragma solidity >=0.6.0 <0.8.0;
+
+/**
+ * @dev Interface of the ERC165 standard, as defined in the
+ * https://eips.ethereum.org/EIPS/eip-165[EIP].
+ *
+ * Implementers can declare support of contract interfaces, which can then be
+ * queried by others ({ERC165Checker}).
+ *
+ * For an implementation, see {ERC165}.
+ */
+interface IERC165 {
+    /**
+     * @dev Returns true if this contract implements the interface defined by
+     * `interfaceId`. See the corresponding
+     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
+     * to learn more about how these ids are created.
+     *
+     * This function call must use less than 30 000 gas.
+     */
+    function supportsInterface(bytes4 interfaceId) external view returns (bool);
+}

contracts/interfaces/IERC721.sol

@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: MIT
+// Taken from OpenZeppelin contracts v3
+
+pragma solidity >=0.6.2 <0.8.0;
+
+import "./IERC165.sol";
+
+/**
+ * @dev Required interface of an ERC721 compliant contract.
+ */
+interface IERC721 is IERC165 {
+    /**
+     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
+     */
+    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
+
+    /**
+     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
+     */
+    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
+
+    /**
+     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
+     */
+    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
+
+    /**
+     * @dev Returns the number of tokens in ``owner``'s account.
+     */
+    function balanceOf(address owner) external view returns (uint256 balance);
+
+    /**
+     * @dev Returns the owner of the `tokenId` token.
+     *
+     * Requirements:
+     *
+     * - `tokenId` must exist.
+     */
+    function ownerOf(uint256 tokenId) external view returns (address owner);
+
+    /**
+     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
+     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
+     *
+     * Requirements:
+     *
+     * - `from` cannot be the zero address.
+     * - `to` cannot be the zero address.
+     * - `tokenId` token must exist and be owned by `from`.
+     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
+     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
+     *
+     * Emits a {Transfer} event.
+     */
+    function safeTransferFrom(address from, address to, uint256 tokenId) external;
+
+    /**
+     * @dev Transfers `tokenId` token from `from` to `to`.
+     *
+     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
+     *
+     * Requirements:
+     *
+     * - `from` cannot be the zero address.
+     * - `to` cannot be the zero address.
+     * - `tokenId` token must be owned by `from`.
+     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
+     *
+     * Emits a {Transfer} event.
+     */
+    function transferFrom(address from, address to, uint256 tokenId) external;
+
+    /**
+     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
+     * The approval is cleared when the token is transferred.
+     *
+     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
+     *
+     * Requirements:
+     *
+     * - The caller must own the token or be an approved operator.
+     * - `tokenId` must exist.
+     *
+     * Emits an {Approval} event.
+     */
+    function approve(address to, uint256 tokenId) external;
+
+    /**
+     * @dev Returns the account approved for `tokenId` token.
+     *
+     * Requirements:
+     *
+     * - `tokenId` must exist.
+     */
+    function getApproved(uint256 tokenId) external view returns (address operator);
+
+    /**
+     * @dev Approve or remove `operator` as an operator for the caller.
+     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
+     *
+     * Requirements:
+     *
+     * - The `operator` cannot be the caller.
+     *
+     * Emits an {ApprovalForAll} event.
+     */
+    function setApprovalForAll(address operator, bool _approved) external;
+
+    /**
+     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
+     *
+     * See {setApprovalForAll}
+     */
+    function isApprovedForAll(address owner, address operator) external view returns (bool);
+
+    /**
+      * @dev Safely transfers `tokenId` token from `from` to `to`.
+      *
+      * Requirements:
+      *
+      * - `from` cannot be the zero address.
+      * - `to` cannot be the zero address.
+      * - `tokenId` token must exist and be owned by `from`.
+      * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
+      * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
+      *
+      * Emits a {Transfer} event.
+      */
+    function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
+}

contracts/interfaces/IERC721Receiver.sol

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: MIT
+// Taken from OpenZeppelin contracts v3
+
+pragma solidity >=0.6.0 <0.8.0;
+
+/**
+ * @title ERC721 token receiver interface
+ * @dev Interface for any contract that wants to support safeTransfers
+ * from ERC721 asset contracts.
+ */
+interface IERC721Receiver {
+    /**
+     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
+     * by `operator` from `from`, this function is called.
+     *
+     * It must return its Solidity selector to confirm the token transfer.
+     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
+     *
+     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
+     */
+    function onERC721Received(address operator, address from, uint256 tokenId, bytes calldata data) external returns (bytes4);
+}

package.json

@@ -60,7 +60,6 @@
     "@nomiclabs/hardhat-etherscan": "^2.1.6",
     "@nomiclabs/hardhat-solhint": "^2.0.0",
     "@nomiclabs/hardhat-waffle": "^2.0.1",
-    "@openzeppelin/contracts": "^3",
     "@sushiswap/bentobox-sdk": "sushiswap/bentobox-sdk#e3f809870b86afbd57e0930662221d2362a160db",
     "@sushiswap/core": "^1.4.2",
     "@tenderly/hardhat-tenderly": "^1.0.12",

yarn.lock

@@ -792,11 +792,6 @@
   resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-3.4.1-solc-0.7-2.tgz#371c67ebffe50f551c3146a9eec5fe6ffe862e92"
   integrity sha512-tAG9LWg8+M2CMu7hIsqHPaTyG4uDzjr6mhvH96LvOpLZZj6tgzTluBt+LsCf1/QaYrlis6pITvpIaIhE+iZB+Q==
 
-"@openzeppelin/contracts@^3":
-  version "3.4.2"
-  resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-3.4.2.tgz#d81f786fda2871d1eb8a8c5a73e455753ba53527"
-  integrity sha512-z0zMCjyhhp4y7XKAcDAi3Vgms4T2PstwBdahiO0+9NaGICQKjynK3wduSRplTgk4LXmoO1yfDGO5RbjKYxtuxA==
-
 "@resolver-engine/core@^0.3.3":
   version "0.3.3"
   resolved "https://registry.yarnpkg.com/@resolver-engine/core/-/core-0.3.3.tgz#590f77d85d45bc7ecc4e06c654f41345db6ca967"