Tune how to get the size of SVG images. Ref https://github.com/GNS3/gns3-gui/issues/2674.

* Default for missing height/width is "100%" as defined in the SVG specification
* Better error message, if viewBox attribute is missing
* Removal of "%" in percent more fault tolerant by using rstrip("%")

gns3server/controller/node.py

@@ -265,7 +265,7 @@ class Node:
         try:
             self._width, self._height, filetype = self._project.controller.symbols.get_size(val)
         except (ValueError, OSError) as e:
-            log.error("Could not write symbol: {}".format(e))
+            log.error("Could not set symbol: {}".format(e))
             # If symbol is invalid we replace it by the default
             self.symbol = ":/symbols/computer.svg"
         if self._label is None: