Check for newlines in project descriptions

As we found out with I88751ed6df7d5f9dad735171e19f82dea745b4da and the
resulting downtime, cgit does not like multi-line description values.
The cgit(5) man page is conspicuously quiet on quoting or multi-line
values; let's just ensure we don't do this again.  This does detect
the newlines in the original change.

Change-Id: I87bcff409d4632c70bff5e4606b4572c38c74e59

tools/check_valid_gerrit_projects.py

@@ -121,6 +121,12 @@ def main():
             (('astor', 'Astor', 'astra', 'Astra', 'astara'), 'Astara')
         )
         if description:
+            # newlines here mess up cgit "repo.desc
+            if '\n' in description:
+                found_errors += 1
+                print("ERROR: Descriptions should not contain newlines:")
+                print('  "%s"' % description)
+
             for words, should_be in badwords:
                 for word in words:
                     # look for the bad word hanging out on it's own.  Only