Create new book fails: "Creation failed, book may already exist!"

Creating a new book fails. As an example, take this guide book for rock climbing. The book exist on amazon,
https://www.amazon.it/Schweiz-Plaisir-sch%C3%B6nsten-Klettereien-Niveau-4a-6a/dp/3906087034

```
ol --create '{"identifiers": {"isbn_10": ["3906087034"]},
"title": "Schweiz Plaisir",
"publisher": "Filidor, Schweiz",
"publish_date": "1993",
"pages": "256",
"author": "Jürg Von Känel"
}'
```
returns
```
Traceback (most recent call last):
File "/usr/local/anaconda3/envs/bibliotek/bin/ol", line 8, in
sys.exit(main())
File "/usr/local/anaconda3/envs/bibliotek/lib/python3.8/site-packages/olclient/cli.py", line 129, in main
edition = ol.Work.create(book)
File "/usr/local/anaconda3/envs/bibliotek/lib/python3.8/site-packages/olclient/openlibrary.py", line 235, in create
ed = cls.OL.create_book(book, debug=debug)
File "/usr/local/anaconda3/envs/bibliotek/lib/python3.8/site-packages/olclient/openlibrary.py", line 935, in create_book
return self._create_book(
File "/usr/local/anaconda3/envs/bibliotek/lib/python3.8/site-packages/olclient/openlibrary.py", line 983, in _create_book
raise ValueError('Creation failed, book may already exist!')
ValueError: Creation failed, book may already exist!
```
Looking at https://openlibrary.org/api/books?bibkeys=ISBN:3906087034&jscmd=data&format=json, we see the book does not exist. Same for google books,
https://www.googleapis.com/books/v1/volumes?q=isbn:3906087034&fields=items/volumeInfo(title,subtitle,authors,publisher,publishedDate,language,industryIdentifiers,pageCount,imageLinks.thumbnail,categories)&maxResults=1

I am using the latest git version. But I get same response using the version from pip.

Am I doing something wrong?

Reproduce the failure with the `ol --create` command and ISBN shown in the issue. Start in `olclient/openlibrary.py`, especially `create_book` and `_create_book`, and trace why the creation response reaches the `ValueError` at line 983. Done means this valid, previously absent book can be created without the reported error.

Written by the indexing model from the issue text.