User assertions do not work anymore

After upgrade to Keybase 1.0.7, user assertions do not work anymore:

$ keybase pgp verify --infile .public_keys/user.key --detached .public_keys/user.key.asc --signed-by "someuser@github || someother@github"
▶ ERROR assertion parse error: Unexpected 'OR' operator

There is really no documentation on this, and in the source code I see:

func NewLexer(s string) *Lexer {
    // We're allowing '||' or ',' for disjunction
    // We're allowing '&&' or '+' for conjunction

So I guess this has been broken.

Reproduce the failure with keybase pgp verify and trace the assertion parser from the NewLexer entry point shown in the issue. Check why || is rejected despite the lexer comment, then verify that the documented disjunction syntax is accepted without the assertion parse error.