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##### SUMMARY
npm doesn't allow "name" arg to be list, gives completely useless, cryptic error when it is

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
npm

##### ANSIBLE VERSION
```paste below
ansible 2.8.1
  config file = /home/jik/src/family-orchestration/ansible.cfg
  configured module search path = [u'/home/jik/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/dist-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.16 (default, Apr  6 2019, 01:42:57) [GCC 8.3.0]
```

##### CONFIGURATION
```paste below
ANSIBLE_PIPELINING(/home/jik/src/family-orchestration/ansible.cfg) = True
DEFAULT_HOST_LIST(/home/jik/src/family-orchestration/ansible.cfg) = [u'/home/jik
DEFAULT_REMOTE_USER(/home/jik/src/family-orchestration/ansible.cfg) = root
```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
Both console and remote ansible host are Ubuntu 19.04 amd64.

##### STEPS TO REPRODUCE

<!--- Paste example playbooks or commands between quotes below -->
```yaml
----
- hosts: localhost
  tasks:
  - npm:
      name:
      - eslint
      - eslint-scope 
```

##### EXPECTED RESULTS
The listed npm packages are installed in a two npm invocations (one to determine which are installed, one to install the missing ones).

##### ACTUAL RESULTS
Completely incomprehensible "ValueError: No JSON object could be decoded" error that doesn't tell you anything about what you're doing wrong or how to fix it.
npm:
    name: coffee-script
    global: yes
- name: Remove the globally package "coffee-script".
  npm:
    name: coffee-script
    global: yes
    state: absent
- name: Install "coffee-script" node.js package from custom registry.
  npm:
    name: coffee-script
    registry: 'http://registry.mysite.com'
- name: Install packages based on package.json.
  npm:
    path: /app/location
- name: Update packages based on package.json to their latest version.
  npm:
    path: /app/location
    state: latest
- name: Install packages based on package.json using the npm installed with nvm v0.10.1.
  npm:
    path: /app/location
    executable: /opt/nvm/v0.10.1/bin/npm
    state: present
'''
import os
import re
from ansible.module_utils.basic import AnsibleModule
import json
class Npm(object):