formatOnType strips spacing around `=` for comma-trailing statements

[brettcannon]

b = {a: b, c: d,
}

becomes:

b={a: b, c: d,
}

[brettcannon]

a = 1,

becomes:

a=1,

[brettcannon]

d= 1, b, c,

becomes:

d=1, b, c,

[brettcannon]

foo = long_function_name(var_one, var_two,
)

becomes:

foo=long_function_name(var_one, var_two,
)

[MikhailArkhipov]

Yep since they look like

foo(a,
b=1,c,
d)