Fix linting error

src/app/files/fileManager.js

@@ -118,9 +118,9 @@ class FileManager extends Plugin {
    * @param {string} path path of the directory or file
    * @returns {boolean} true if the path exists
    */
-  exists(path) {
+  exists (path) {
     const provider = this.fileProviderOf(path)
-    return provider ? true : false
+    return provider ? true : false // eslint-disable-line
   }
 
   /**
@@ -142,7 +142,7 @@ class FileManager extends Plugin {
   open (path) {
     this._handleExists(path, `Cannot open file ${path}`)
     this._handleIsFile(path, `Cannot open file ${path}`)
-    this.switchFile(path)
+    return this.switchFile(path)
   }
 
   /**
@@ -187,7 +187,7 @@ class FileManager extends Plugin {
    * @note will not work on a directory, use `rmdir` instead
    * @returns {void}
    */
-  unlink(path) {
+  unlink (path) {
     this._handleExists(path, `Cannot remove file ${path}`)
     this._handleIsDir(path, `Cannot remove file ${path}`)
   }
@@ -242,7 +242,7 @@ class FileManager extends Plugin {
    * @note will not work on a file, use `unlink` instead
    * @returns {void}
    */
-  rmdir(path) {
+  rmdir (path) {
     this._handleExists(path, `Cannot remove directory ${path}`)
     this._handleIsDir(path, `Cannot remove directory ${path}`)
     // To implement