fix(import): remove usage of stream.finished

- stream.finished wasn't added until node v10

lib/tasks/import/api.js

@@ -1,14 +1,10 @@
 const fs = require('fs-extra');
 const got = require('got');
 const get = require('lodash/get');
-const util = require('util');
-const stream = require('stream');
 const semver = require('semver');
 const FormData = require('form-data');
 const {Cookie} = require('tough-cookie');
 
-const finished = util.promisify(stream.finished);
-
 const {SystemError} = require('../../errors');
 
 const bases = {
@@ -103,10 +99,12 @@ async function runImport(version, url, auth, exportFile) {
 async function downloadExport(version, url, auth, outputFile) {
     const authOpts = await getAuthOpts(version, url, auth);
 
-    const ws = fs.createWriteStream(outputFile);
-    const resp = got.stream('/db/', {...authOpts}).pipe(ws);
+    await new Promise((resolve, reject) => {
+        const ws = fs.createWriteStream(outputFile);
+        const resp = got.stream('/db/', {...authOpts}).pipe(ws);
 
-    await finished(resp);
+        resp.on('finish', () => resolve()).on('error', reject);
+    });
 }
 
 module.exports = {