Add yappi dependency for "nilmdb-server -y", but don't require ipython

nilmdb/scripts/nilmdb_server.py

@@ -78,9 +78,12 @@ def main():
                 stats = yappi.get_func_stats()
                 stats.sort("ttot")
                 stats.print_all()
-                from IPython import embed
-                embed(header="Use the `yappi` or `stats` object to explore "
+                try:
+                    from IPython import embed
+                    embed(header="Use the `yappi` or `stats` object to explore "
                       "further, quit to exit")
+                except ModuleNotFoundError:
+                    print("\nInstall ipython to explore further")
         else:
             server.start(blocking=True)
     except nilmdb.server.serverutil.CherryPyExit:

requirements.txt

@@ -13,7 +13,7 @@ python-datetime-tz==0.5.4
 python-dateutil==2.8.1
 requests==2.24.0
 tz==0.2.2
-WebTest==2.0.35
+yappi==1.2.5
 
 ## The following requirements were added by pip freeze:
 beautifulsoup4==4.9.1
@@ -37,4 +37,5 @@ tempora==4.0.0
 urllib3==1.25.10
 waitress==1.4.4
 WebOb==1.8.6
+WebTest==2.0.35
 zc.lockfile==2.0