Fix bad zip file issue with GEE API

[pasquierjb]

File "../Src/img_lib.py", line 183, in download_images
self._save_img(url, self.image_dir, file_name, provider)
File "../Src/img_lib.py", line 238, in _save_img
gee_tif = sentinel_utils.download_and_unzip(buffer, 3, 6, file_path)
File "../Src/sentinel_utils.py", line 88, in download_and_unzip
zip_file = ZipFile(buffer)
File "/home/anaconda3/envs/HRM/lib/python3.5/zipfile.py", line 1026, in init
self._RealGetContents()
File "/home/anaconda3/envs/HRM/lib/python3.5/zipfile.py", line 1093, in _RealGetContents
raise BadZipFile("File is not a zip file")
zipfile.BadZipFile: File is not a zip file