Bug 1369710 - [mozlint] Ensure that a valid path is entered. r=ahal

MozReview-Commit-ID: 6HOE9hmOkCx

--HG--
extra : rebase_source : 584a4391b832e794dc084254e9203b3a65c89419

python/mozlint/mozlint/cli.py

@@ -113,6 +113,12 @@ def run(paths, linters, fmt, outgoing, workdir, **lintargs):
     lint = LintRoller(**lintargs)
     lint.read(find_linters(linters))
 
+    # Check if the path that is entered is a valid one.
+    invalid_paths = [path for path in paths if not os.path.exists(path)]
+    if invalid_paths:
+        print("Error: The following paths do not exist:\n{}".format("\n".join(invalid_paths)))
+        return 1
+
     # run all linters
     results = lint.roll(paths, outgoing=outgoing, workdir=workdir)
     formatter = formatters.get(fmt)