Added PausablePool contract to support errors by number.

contracts/lendingpool/LendingPool.sol

@@ -4,7 +4,6 @@ pragma experimental ABIEncoderV2;
 
 import {SafeMath} from '@openzeppelin/contracts/math/SafeMath.sol';
 import {IERC20} from '@openzeppelin/contracts/token/ERC20/IERC20.sol';
-import {Pausable} from '@openzeppelin/contracts/utils/Pausable.sol';
 import {
   VersionedInitializable
 } from '../libraries/openzeppelin-upgradeability/VersionedInitializable.sol';
@@ -25,6 +24,7 @@ import {LendingPoolLiquidationManager} from './LendingPoolLiquidationManager.sol
 import {IPriceOracleGetter} from '../interfaces/IPriceOracleGetter.sol';
 import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import {ILendingPool} from '../interfaces/ILendingPool.sol';
+import {PausablePool} from '../misc/PausablePool.sol';
 
 /**
  * @title LendingPool contract
@@ -32,7 +32,7 @@ import {ILendingPool} from '../interfaces/ILendingPool.sol';
  * @author Aave
  **/
 
-contract LendingPool is VersionedInitializable, Pausable, ILendingPool {
+contract LendingPool is VersionedInitializable, PausablePool, ILendingPool {
   using SafeMath for uint256;
   using WadRayMath for uint256;
   using ReserveLogic for ReserveLogic.ReserveData;
@@ -929,9 +929,9 @@ contract LendingPool is VersionedInitializable, Pausable, ILendingPool {
   }
 
   /**
-   * @dev Returns true if the contract is paused, and false otherwise.
+   * @dev retrieve pause status
    */
   function isPaused() public override view returns (bool) {
-    return Pausable.paused();
+    return PausablePool.paused();
   }
 }

contracts/libraries/helpers/Errors.sol

@@ -46,8 +46,8 @@ library Errors {
   string public constant CANNOT_GIVE_ALLOWANCE_TO_HIMSELF = '30'; // 'User cannot give allowance to himself'
   string public constant TRANSFER_AMOUNT_NOT_GT_0 = '31'; // 'Transferred amount needs to be greater than zero'
   string public constant INVALID_ATOKEN_BALANCE = '52'; // balance on burning is invalid
-  
-   // require error messages - ReserveLogic
+
+  // require error messages - ReserveLogic
   string public constant RESERVE_ALREADY_INITIALIZED = '34'; // 'Reserve has already been initialized'
   string public constant LIQUIDITY_INDEX_OVERFLOW = '47'; //  Liquidity index overflows uint128
   string public constant VARIABLE_BORROW_INDEX_OVERFLOW = '48'; //  Variable borrow index overflows uint128
@@ -73,4 +73,8 @@ library Errors {
   string public constant MULTIPLICATION_OVERFLOW = '44';
   string public constant ADDITION_OVERFLOW = '45';
   string public constant DIVISION_BY_ZERO = '46';
+
+  // pausable error message
+  string public constant IS_PAUSED = '54'; // 'Pool is paused'
+  string public constant IS_ACTIVE = '55'; // 'Pool is active'
 }

contracts/misc/PausablePool.sol

@@ -0,0 +1,88 @@
+pragma solidity ^0.6.0;
+
+import {Context} from './Context.sol';
+
+/**
+ * @dev Contract module which allows children to implement an emergency stop
+ * mechanism that can be triggered by an authorized account.
+ *
+ * This module is used through inheritance. It will make available the
+ * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
+ * the functions of your contract. Note that they will not be pausable by
+ * simply including this module, only once the modifiers are put in place.
+ */
+contract PausablePool is Context {
+  /**
+   * @dev Emitted when the pause is triggered by `account`.
+   */
+  event Paused(address account);
+
+  /**
+   * @dev Emitted when the pause is lifted by `account`.
+   */
+  event Unpaused(address account);
+
+  bool private _paused;
+
+  /**
+   * @dev Initializes the contract in unpaused state.
+   */
+  constructor() internal {
+    _paused = false;
+  }
+
+  /**
+   * @dev Returns true if the contract is paused, and false otherwise.
+   */
+  function paused() public virtual view returns (bool) {
+    return _paused;
+  }
+
+  /**
+   * @dev Modifier to make a function callable only when the contract is not paused.
+   *
+   * Requirements:
+   *
+   * - The contract must not be paused.
+   */
+  modifier whenNotPaused() {
+    require(!_paused, '54');
+    _;
+  }
+
+  /**
+   * @dev Modifier to make a function callable only when the contract is paused.
+   *
+   * Requirements:
+   *
+   * - The contract must be paused.
+   */
+  modifier whenPaused() {
+    require(_paused, '55');
+    _;
+  }
+
+  /**
+   * @dev Triggers stopped state.
+   *
+   * Requirements:
+   *
+   * - The contract must not be paused.
+   */
+  function _pause() internal virtual whenNotPaused {
+    _paused = true;
+    emit Paused(_msgSender());
+  }
+
+  /**
+   * @dev Returns to normal state.
+   *
+   * Requirements:
+   *
+   * - The contract must be paused.
+   */
+  function _unpause() internal virtual whenPaused {
+    _paused = false;
+    emit Unpaused(_msgSender());
+  }
+}

helpers/types.ts

@@ -99,7 +99,8 @@ export enum ProtocolErrors {
   NO_ERRORS = '42', // 'No errors'
   INVALID_FLASHLOAN_MODE = '43', //Invalid flashloan mode
 
-  IS_PAUSED = 'Pausable: paused',
+  IS_PAUSED = '54', // Pool is paused
+  IS_ACTIVE = '55', // Pool is active
 
   // old