helpful error message for empty path "d" attribute (fixes #220)

also internationalizes "error:" string

lib/elements/element.py

@@ -197,7 +197,11 @@ class EmbroideryElement(object):
         # In a path, each element in the 3-tuple is itself a tuple of (x, y).
         # Tuples all the way down.  Hasn't anyone heard of using classes?
 
-        return cubicsuperpath.parsePath(self.node.get("d"))
+        d = self.node.get("d", "")
+        if not d:
+            self.fatal(_("Object %(id)s has an empty 'd' attribute.  Please delete this object from your document.") % dict(id=self.node.get("id")))
+
+        return cubicsuperpath.parsePath(d)
 
     @cache
     def parse_path(self):
@@ -264,5 +268,7 @@ class EmbroideryElement(object):
         return patches
 
     def fatal(self, message):
-        print >> sys.stderr, "error:", message
+        # L10N used when showing an error message to the user such as "satin column: One or more of the rungs doesn't
+        # intersect both rails."
+        print >> sys.stderr, _("error:"), message
         sys.exit(1)

messages.po

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PROJECT VERSION\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2018-08-24 20:56-0400\n"
+"POT-Creation-Date: 2018-08-24 21:20-0400\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -178,11 +178,25 @@ msgid ""
 "shapes."
 msgstr ""
 
-#: lib/elements/element.py:230
+#: lib/elements/element.py:202
+#, python-format
+msgid ""
+"Object %(id)s has an empty 'd' attribute.  Please delete this object from"
+" your document."
+msgstr ""
+
+#: lib/elements/element.py:234
 #, python-format
 msgid "%(id)s has more than one command of type '%(command)s' linked to it"
 msgstr ""
 
+#. used when showing an error message to the user such as "satin column: One or
+#. more of the rungs doesn't
+#. intersect both rails."
+#: lib/elements/element.py:273
+msgid "error:"
+msgstr ""
+
 #: lib/elements/fill.py:12
 msgid "Fill"
 msgstr ""