More Readable Pyang Error Lines

[wenovus]

Sample output:

line 118: type "ocinet:ip-prefix" rejected valid pattern: "192.0.2.1/32"
line 120: type "ocinet:ip-prefix" rejected valid pattern: "FE80::CAFE/128"
line 125: type "ocinet:domain-name" rejected valid pattern: "ambroseesorbma"
line 127: type "ocinet:domain-name" rejected valid pattern: "claire."
line 130: type "ocinet:domain-name" rejected valid pattern: "012345678901234567890123456789012345678901234567890123456789012."
line 135: type "oc-pkt-match-types:port-num-range" rejected valid pattern: "0..0"
line 136: type "oc-pkt-match-types:port-num-range" rejected valid pattern: "00000..00000"
line 137: type "oc-pkt-match-types:port-num-range" rejected valid pattern: "00..00"
line 138: type "oc-pkt-match-types:port-num-range" rejected valid pattern: "01..01"

It's possible to improve it even more by outputting to a textproto for unmarshalling, but I feel this is 80% of the way there.

[wenovus]

Optimistically merging: see sample output at https://gist.github.com/OpenConfigBot/b4486f4ca61fe5111778f5e3da267fd4

[robshakir]

Please don't merge code that hasn't been reviewed. I'll change this repo to require code reviews, I'd like to keep a consistent strategy here -- we should only force merge when there is a key requirement to do so.

[wenovus]

OK got it.