Clean Code: Python

Fix issues found by flake8-bugbear:

* Unused loop variables
* assert statements in non-test code
* mixing test code with production code
* mark one excessive test which takes ~10min to run
  as 'slow'

84_Super_Star_Trek/python/superstartrek.py

@@ -882,7 +882,7 @@ def new_quadrant():
     if b3 > 0:
         b4, b5 = find_empty_place()  # position of starbase (sector)
         insert_marker(b4, b5, ">!<")
-    for i in range(s3):
+    for _ in range(s3):
         r1, r2 = find_empty_place()
         insert_marker(r1, r2, " * ")