Add num_convert.py to the starter code, chapter 10. It's absence watch causing confusion.

Author: mikeckennedy

app/ch10_using_sqlachemy/starter/pypi_org/infrastructure/num_convert.py

@@ -0,0 +1,5 @@
+def try_int(text) -> int:
+    try:
+        return int(text)
+    except:
+        return 0