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, " * ")
 

84_Super_Star_Trek/python/superstartrekins.py

@@ -14,7 +14,7 @@ def get_yes_no(prompt):
 
 
 def print_header():
-    for i in range(12):
+    for _ in range(12):
         print()
     t10 = " " * 10
     print(t10 + "*************************************")
@@ -24,7 +24,7 @@ def print_header():
     print(t10 + "*                                   *")
     print(t10 + "*                                   *")
     print(t10 + "*************************************")
-    for i in range(8):
+    for _ in range(8):
         print()