Incorrect stripping of leading quote in env var

[stevejalim]

I think I've uncovered a corner-case bug with quotes.

Specifically, if an env var string starts with a quote mark, that leading quote gets stripped.

It's not a common situation, but this came up when tinkering with CSP rules, which provides a reasonable example.

In my Python code, I'm parsing env vars with this setup:

config = ConfigManager(
    [
        ConfigOSEnv(),
        ConfigEnvFileEnv(".env"),
    ]
)
...

CSP_SCRIPT_SRC = config("CSP_SCRIPT_SRC", default='unimportant for this example', parser=str)

My .env file has the following:

CSP_SCRIPT_SRC="'self' www.googletagmanager.com"

And the parsed value ends up being self' www.googletagmanager.com -- which is invalid as a CSP rule because it needs to be 'self' with quotes

However, if I add a space between the opening " and ' in my .env file, the over-stripping doesn't occur:

CSP_SCRIPT_SRC=" 'self' www.googletagmanager.com"

Parsed value: 'self' www.googletagmanager.com