volume sharing not working in docker

[irene]

Permission errors exist when trying to share volumes

$ docker-compose up

Log:

```
Starting mediagoblin_web_1
Attaching to mediagoblin_web_1
web_1  | Using paster config: paste.ini
web_1  | Using ./bin/paster
web_1  | + export CELERY_ALWAYS_EAGER=true
web_1  | + ./bin/paster serve paste.ini --server-name=broadcast --reload
web_1  | 2021-03-06 02:46:32,608 INFO    [mediagoblin.app] GNU MediaGoblin 
0.11.dev main server starting
web_1  | Traceback (most recent call last):
web_1  |   File "/opt/mediagoblin/mediagoblin/tools/crypto.py", line 81, in 
setup_crypto
web_1  |     load_key(key_filepath)
web_1  |   File "/opt/mediagoblin/mediagoblin/tools/crypto.py", line 45, in 
load_key
web_1  |     key_file = open(filename)
web_1  | FileNotFoundError: [Errno 2] No such file or directory: 
'/opt/mediagoblin/user_dev/crypto/itsdangeroussecret.bin'
web_1  | 
web_1  | During handling of the above exception, another exception occurred:
web_1  | 
web_1  | Traceback (most recent call last):
web_1  |   File "/opt/mediagoblin/./bin/paster", line 11, in <module>
web_1  |     load_entry_point('PasteScript', 'console_scripts', 'paster')()
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteScript-2.0.2-py3.9.egg/paste/script/command.py",
 line 102, in run
web_1  |     invoke(command, command_name, options, args[1:])
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteScript-2.0.2-py3.9.egg/paste/script/command.py",
 line 141, in invoke
web_1  |     exit_code = runner.run(args)
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteScript-2.0.2-py3.9.egg/paste/script/command.py",
 line 236, in run
web_1  |     result = self.command()
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteScript-2.0.2-py3.9.egg/paste/script/serve.py",
 line 283, in command
web_1  |     app = self.loadapp(app_spec, name=app_name,
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteScript-2.0.2-py3.9.egg/paste/script/serve.py",
 line 327, in loadapp
web_1  |     return loadapp(
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteDeploy-2.1.1-py3.9.egg/paste/deploy/loadwsgi.py",
 line 253, in loadapp
web_1  |     return loadobj(APP, uri, name=name, **kw)
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteDeploy-2.1.1-py3.9.egg/paste/deploy/loadwsgi.py",
 line 278, in loadobj
web_1  |     return context.create()
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteDeploy-2.1.1-py3.9.egg/paste/deploy/loadwsgi.py",
 line 715, in create
web_1  |     return self.object_type.invoke(self)
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteDeploy-2.1.1-py3.9.egg/paste/deploy/loadwsgi.py",
 line 209, in invoke
web_1  |     app = context.app_context.create()
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteDeploy-2.1.1-py3.9.egg/paste/deploy/loadwsgi.py",
 line 715, in create
web_1  |     return self.object_type.invoke(self)
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteDeploy-2.1.1-py3.9.egg/paste/deploy/loadwsgi.py",
 line 152, in invoke
web_1  |     return fix_call(context.object, context.global_conf, 
**context.local_conf)
web_1  |   File 
"/opt/mediagoblin/lib/python3.9/site-packages/PasteDeploy-2.1.1-py3.9.egg/paste/deploy/util.py",
 line 55, in fix_call
web_1  |     val = callable(*args, **kw)
web_1  |   File "/opt/mediagoblin/mediagoblin/app.py", line 366, in 
paste_app_factory
web_1  |     mgoblin_app = MediaGoblinApp(mediagoblin_config)
web_1  |   File "/opt/mediagoblin/mediagoblin/app.py", line 96, in __init__
web_1  |     setup_crypto(self.app_config)
web_1  |   File "/opt/mediagoblin/mediagoblin/tools/crypto.py", line 85, in 
setup_crypto
web_1  |     create_key(key_dir, key_filepath)
web_1  |   File "/opt/mediagoblin/mediagoblin/tools/crypto.py", line 58, in 
create_key
web_1  |     os.makedirs(key_dir)
web_1  |   File "/usr/lib/python3.9/os.py", line 225, in makedirs
web_1  |     mkdir(name, mode)
web_1  | PermissionError: [Errno 13] Permission denied: 
'/opt/mediagoblin/user_dev/crypto'
web_1  | Starting subprocess with file monitor
mediagoblin_web_1 exited with code 0
```