Have a default set of linting rules

[brettcannon]

The default rules for most linters like pylint are rather broad and thus can be annoying if you only want squiggles for basic stuff like unused variables (e.g. not everyone wants to be told what an appropriate variable name is). When the user doesn't provide any specific linting configuration -- whether through a config file or through their settings.json -- we should provide a default experience that works for the vast majority of users to keep them from being overwhelmed.

[brettcannon]

Our current thinking is to enable all F and E messages (fatal and error, respectively), and the following warnings:

• unreachable (W0101): Unreachable code
• duplicate-key (W0109): Duplicate key %r in dictionary
• unnecessary-semicolon (W0301): Unnecessary semicolon
• global-variable-not-assigned (W0602): Using global for %r but no assignment is done
• unused-variable (W0612): Unused variable %r
• binary-op-exception (W0711): Exception to catch is the result of a binary "%s" operation
• bad-format-string (W1302): Invalid format string
• anomalous-backslash-in-string (W1401): Anomalous backslash in string
• bad-open-mode (W1501): "%s" is not a valid mode for open

The --enable flag to Pylint should make this straightforward in that regard, e.g. --enable=F,E,W0602,....

[brettcannon]

Here are the settings I have in my own settings.json to make the proposal work:

"python.linting.enabled": true,
    "python.linting.pylintEnabled": true,
    // Unnecessary once https://github.com/Microsoft/vscode-python/issues/554 is fixed.
    "python.linting.pylintArgs": [
        "--disable=all",
        "--enable=F,E,unreachable,duplicate-key,unnecessary-semicolon,global-variable-not-assigned,unused-variable,binary-op-exception,bad-format-string,anomalous-backslash-in-string,bad-open-mode"
    ]

[MikhailArkhipov]

df39217