Fix latest migration failures (#2227)

We've seen a surge of migration failures with the last release which
includes a migration making network requests.

This PR aims at preventing these failures and making sure Sentry
exceptions include more details to help us debug migration errors in the
future.

core/migrations/migrations.js

@@ -4,6 +4,7 @@
  */
 
 const path = require('path')
+const { Promise } = require('bluebird')
 
 const metadata = require('../metadata')
 const { SCHEMA_INITIAL_VERSION } = require('./constants')
@@ -352,8 +353,9 @@ module.exports = ([
       docs /*: SavedMetadata[] */,
       { remote } /*: InjectedDependencies */
     ) /*: Promise<SavedMetadata[]> */ => {
-      return Promise.all(
-        docs.map(async doc => {
+      return Promise.map(
+        docs,
+        async doc => {
           const remoteDir = await remote.remoteCozy.findDir(doc.remote._id)
 
           if (remoteDir != null) {
@@ -400,7 +402,10 @@ module.exports = ([
           }
 
           return doc
-        })
+        },
+        // XXX: Avoid exhausting network resources by limiting the number of
+        // concurrent requests.
+        { concurrency: 10 }
       )
     }
   }

core/utils/sentry.js

@@ -105,7 +105,6 @@ const handleBunyanMessage = msg => {
   // Send messages explicitly marked for sentry and all TypeError instances
   if (msg.sentry || (msg.err && msg.err.name === 'TypeError')) {
     const extra = _.omit(msg, [
-      'err',
       'tags',
       'v',
       'hostname',

gui/main.js

@@ -20,7 +20,7 @@ const {
   SYNC_DIR_EMPTY_MESSAGE,
   SYNC_DIR_UNLINKED_MESSAGE
 } = require('../core/local/errors')
-const { MigrationFailedError } = require('../core/migrations/migrations')
+const { MigrationFailedError } = require('../core/migrations')
 const config = require('../core/config')
 const winRegistry = require('../core/utils/win_registry')