jw.pkg.lib.util.run_curl(): Beautify logging

Make some incomprensible parser error messages if run_curl() returns
nothing slightly less incomprehensible.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/util.py

@@ -230,12 +230,13 @@ async def run_curl(args: list[str], parse_json: bool=True, wd=None, throw=None,
         try:
             return json.loads(ret)
         except Exception as e:
-            size = 'None'
+            size = 'unknown number of'
             try:
                 size = len(ret)
             except:
                 pass
-            print(f'Failed to parse {size} bytes output of command >{pretty_cmd(cmd, wd)}< ({str(e)})', file=sys.stderr)
+            print(f'Failed to parse {size} bytes output of command '
+                  + f'>{pretty_cmd(cmd, wd)}< ({str(e)}): "{ret}"', file=sys.stderr)
             raise
     return ret