Change how python tests are executed

Require them to have assert rather than testing the
result variables set.

This makes for way simpler code.

Now also prints stacktrace to know where the problem occurred.

test/rename_insert1.py

@@ -1,5 +1,4 @@
 p1=people.rename({"id":"ido"})
 people.insert((123,"lala",0,31))
-
-retval=people==p1
+assert people!=p1
 people.delete("id==123")

test/rename_insert1.result

@@ -1 +0,0 @@
-{'retval':False}

test/rename_insert2.py

@@ -1,5 +1,4 @@
 p1=people.rename({"id":"ido"})
 p1.insert((123,"lala",0,31))
-
-retval=people==p1
+assert people!=p1
 people.delete("id==123")

test/rename_insert2.result

@@ -1 +0,0 @@
-{'retval':False}