Schlib: Check for space separated keywords

Check if the keywords contain 'evil' characters. We don't want commas or
dots but spaces instead. Try to handle special cases like '3.3V' where a
dot is allowed.

Resolves: KiCad#321

schlib/rules/S6_2.py

@@ -134,6 +134,13 @@ def checkKeywords(self):
             else:
                 self.error("Missing Keywords field on 'Properties' tab")
                 return True
+        else:
+            # find special chars.
+            # a dot followed by a non-word char is also considered a violation. This allows 3.3V but prevents 'foobar. buzz'
+            forbidden_matches = re.findall('\.\W|\.$|[,:;?!<>]', keywords)
+            if forbidden_matches:
+                errors.append("Symbol keywords contain forbidden symbols: {}".format(forbidden_matches))
+                return True
 
         return False