Fix messages for file lookup issues - error scenario (#3654); see #3646

Scenario where multiple files (all) are not found only show a single message.
I feel its useful for debugging to keep the message if only 1 file is not found. Happy to remove if others don't agree.

No changes where at least 1 is found (still prints msg).

See PR #3650 for full details

## Scenarios

### Nothing given
Command: `mocha`
Output:
```
Error: No test files found: "test/"
```

### Nothing found
Command: `mocha -R json-stream --no-config "test/integration/fixtures/glob/**/*-none.js"`
Output:
```
Error: No test files found: "test/integration/fixtures/glob/**/*-none.js"
```

### Multiple not found
Command: `mocha -R json-stream --no-config "test/integration/fixtures/glob/**/*-none.js" "test/integration/fixtures/glob/**/*-none-again.js"`
New output
```
Error: No test files found
```
Previous output
```
Error: Cannot find any files matching pattern "test/integration/fixtures/glob/**/*-none.js"
Error: Cannot find any files matching pattern "test/integration/fixtures/glob/**/*-none-again.js"
```

## Applicable issues
(semver-patch)

lib/cli/run-helpers.js

@@ -137,14 +137,14 @@ exports.handleFiles = ({
   spec = []
 } = {}) => {
   let files = [];
-  const errors = [];
+  const unmatched = [];
   spec.forEach(arg => {
     let newFiles;
     try {
       newFiles = utils.lookupFiles(arg, extension, recursive);
     } catch (err) {
       if (err.code === 'ERR_MOCHA_NO_FILES_MATCH_PATTERN') {
-        errors.push(err.message);
+        unmatched.push({message: err.message, pattern: err.pattern});
         return;
       }
 
@@ -164,15 +164,17 @@ exports.handleFiles = ({
   });
 
   if (!files.length) {
-    // print messages as an error
-    errors.forEach(message => {
-      console.error(ansi.red(`Error: ${message}`));
-    });
+    // give full message details when only 1 file is missing
+    const noneFoundMsg =
+      unmatched.length === 1
+        ? `Error: No test files found: ${JSON.stringify(unmatched[0].pattern)}` // stringify to print escaped characters raw
+        : 'Error: No test files found';
+    console.error(ansi.red(noneFoundMsg));
     process.exit(1);
   } else {
     // print messages as an warning
-    errors.forEach(message => {
-      console.warn(ansi.yellow(`Warning: ${message}`));
+    unmatched.forEach(warning => {
+      console.warn(ansi.yellow(`Warning: ${warning.message}`));
     });
   }
 

test/integration/glob.spec.js

@@ -28,13 +28,24 @@ describe('globbing', function() {
           expect(
             results.stderr,
             'to contain',
-            'Error: Cannot find any files matching pattern "./*-none.js"'
+            'Error: No test files found: "./*-none.js"'
           );
         },
         done
       );
     });
 
+    it('should handle multiple non-matching patterns', function(done) {
+      testGlob.shouldFail(
+        './*-none.js ./*-none-twice.js',
+        function(results) {
+          expect(results.stderr, 'to contain', 'Error: No test files found');
+          expect(results.stderr, 'not to contain', '*-none');
+        },
+        done
+      );
+    });
+
     it('should handle both matching and non-matching patterns in the same command', function(done) {
       testGlob.shouldSucceed(
         './*.js ./*-none.js',
@@ -77,13 +88,23 @@ describe('globbing', function() {
           expect(
             results.stderr,
             'to contain',
-            'Error: Cannot find any files matching pattern "./*-none.js"'
+            'Error: No test files found: "./*-none.js"'
           );
         },
         done
       );
     });
 
+    it('should handle multiple non-matching patterns', function(done) {
+      testGlob.shouldFail(
+        '"./*-none.js" "./*-none-twice.js"',
+        function(results) {
+          expect(results.stderr, 'to contain', 'Error: No test files found');
+        },
+        done
+      );
+    });
+
     it('should handle both matching and non-matching patterns in the same command', function(done) {
       testGlob.shouldSucceed(
         '"./*.js" "./*-none.js"',
@@ -125,7 +146,7 @@ describe('globbing', function() {
             expect(
               results.stderr,
               'to contain',
-              'Error: Cannot find any files matching pattern "./**/*-none.js"'
+              'Error: No test files found: "./**/*-none.js"'
             );
           },
           done