Better Handle Errors Thrown When Looking for a Deleted/Missing Pattern

[bmuenzenmeyer]

Pattern Lab is quite unforgiving when it fails to find a pattern that does not exist, usually throwing a cryptic error message.

We should better wrap and handle this scenario and tell users what pattern the engine is lookin for.

[NickToye]

A recent error I received.

{ SyntaxError: Unexpected 'u' at line 1 column 2 of the JSON5 data. Still to read: "undefined"
at error (/Users/nicktoye/Dev/edition-node-gulp/node_modules/json5/lib/json5.js:56:25)
at word (/Users/nicktoye/Dev/edition-node-gulp/node_modules/json5/lib/json5.js:393:13)
at value (/Users/nicktoye/Dev/edition-node-gulp/node_modules/json5/lib/json5.js:493:56)
at Object.parse (/Users/nicktoye/Dev/edition-node-gulp/node_modules/json5/lib/json5.js:508:18)
at expandPartials (/Users/nicktoye/Dev/edition-node-gulp/node_modules/patternlab-node/core/lib/pattern_assembler.js:431:39)
at decomposePattern (/Users/nicktoye/Dev/edition-node-gulp/node_modules/patternlab-node/core/lib/pattern_assembler.js:229:7)
at processPatternRecursive (/Users/nicktoye/Dev/edition-node-gulp/node_modules/patternlab-node/core/lib/pattern_assembler.js:395:5)
at Object.process_pattern_recursive (/Users/nicktoye/Dev/edition-node-gulp/node_modules/patternlab-node/core/lib/pattern_assembler.js:542:7)
at /Users/nicktoye/Dev/edition-node-gulp/node_modules/patternlab-node/core/lib/patternlab.js:59:25
at /Users/nicktoye/Dev/edition-node-gulp/node_modules/diveSync/diveSync.js:57:18
message: 'Unexpected 'u' at line 1 column 2 of the JSON5 data. Still to read: "undefined"',
at: 1,
lineNumber: 1,
columnNumber: 2 }