Improve invalid package name errors

[patrickkettner]

Notcied a number of issues cropping up that boiled down to how bad the error message is, this attempts to fix that.

[desandro]

Oh rad. One suggestion - could return multiple errors if the package name fails on multiple rules?

[patrickkettner]

yes. yes i could.

[patrickkettner]

these are all of the possible generated values - any copy suggestions?

Package names must be between 1 and 50 characters.                               
Package names must only contain lower case a through z, 0 through 9, dots, dashes, and underscores.
Package names must not have consecutive dashes, dots, or underscores.            
Package names must not start or end with dashes, dots, or underscores.           
Package names must be between 1 and 50 characters, and must only contain lower case a through z, 0 through 9, dots, dashes, and underscores.
Package names must be between 1 and 50 characters, and must not have consecutive dashes, dots, or underscores.
Package names must be between 1 and 50 characters, and must not start or end with dashes, dots, or underscores.
Package names must only contain lower case a through z, 0 through 9, dots, dashes, and underscores, and must not have consecutive dashes, dots, or underscores.
Package names must only contain lower case a through z, 0 through 9, dots, dashes, and underscores, and must not start or end with dashes, dots, or underscores.
Package names must not have consecutive dashes, dots, or underscores, and must not start or end with dashes, dots, or underscores.
Package names must be between 1 and 50 characters, only contain lower case a through z, 0 through 9, dots, dashes, and underscores, and must not have consecutive dashes, dots, or underscores.
Package names must be between 1 and 50 characters, not have consecutive dashes, dots, or underscores, and must not start or end with dashes, dots, or underscores.
Package names must be between 1 and 50 characters, only contain lower case a through z, 0 through 9, dots, dashes, and underscores, and must not start or end with dashes, dots, or underscores.
Package names must only contain lower case a through z, 0 through 9, dots, dashes, and underscores, not have consecutive dashes, dots, or underscores, and must not start or end with dashes, dots, or underscores.
Package names must be between 1 and 50 characters, only contain lower case a through z, 0 through 9, dots, dashes, and underscores, not have consecutive dashes, dots, or underscores, and must not start or end with dashes, dots, or underscores.

[rayshan]

Should we loop through errors? If there are 3 errors, this only modifies the 2nd one but not the 3rd one.

[rayshan]

nevermind i just reviewed the copy, it makes sense

[rayshan]

Thanks! copy looks good. overall lgtm.

[patrickkettner]

@desandro - you good?

[desandro]

thumbs up

[rayshan]

deployed, thanks @patrickkettner @desandro

[paulirish]

Yay for communicative error messages! nice one @patrickkettner