ENOENT: no such file or directory, open

Hello,

I'm using [react-native-document-picker](https://github.com/rnmods/react-native-document-picker) in order to pick an audio file.

After this i'm using `RNFS.readFile(nft.teaser.url, 'base64')` to obtain a base64 that should be upload in a blob.

The problem is that RNFS.readFile throws an exception:

```
Error: ENOENT: no such file or directory, open '/Users/xxx/Library/Developer/CoreSimulator/Devices/F21F02D1-2AEE-4DDE-A5DA-B8EEE28073FB/data/Containers/Data/Application/C33F0FAE-C0F5-429A-9CCB-FF7A5E586381/tmp/yyyy-Inbox/file_example_MP3_700KB%20(1).mp3'
at fn (NativeModules.js:99)
at readFileGeneric (FS.common.js:160)
at Object.readFile (FS.common.js:310)
at _callee4$ (VM13 actions.bundle:194)
at tryCatch (runtime.js:63)
at Generator.invoke [as _invoke] (runtime.js:293)
at Generator.next (runtime.js:118)
at tryCatch (runtime.js:63)
at invoke (runtime.js:154)
at runtime.js:189
```
It's strange because the path I pass to readFile begins with "files//" and in exception looks like this part was removed from the path.

Any help would be appreciated.

Thanks!