remove last references to Python 2

Author: mr-c

tests/args.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 import sys
 import json
 import os

tests/cat1-testcli.cwl

@@ -6,7 +6,7 @@
     "hints": [
         {
             "class": "DockerRequirement",
-            "dockerPull": "python:2-slim"
+            "dockerPull": "python:3-slim"
         }
     ],
     "inputs": [

tests/index.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 
 # Toy program to generate inverted index of word to line.
 # Takes input text file on stdin and prints output index on stdout.

tests/search.py

@@ -1,10 +1,8 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Toy program to search inverted index and print out each line the term
 # appears.
 
-from __future__ import print_function
-
 import sys
 
 mainfile = sys.argv[1]
@@ -23,5 +21,5 @@
         for l in main:
             linenum += 1
             if linenum in n:
-                print(linenum, l.rstrip())
+                print(f"{linenum} {l.rstrip()}")
         break

tests/subdirsecondaries/index.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 
 # Toy program to generate inverted index of word to line.
 # Takes input text file on stdin and prints output index on stdout.

tests/tmap-tool.cwl

@@ -6,7 +6,7 @@
     "hints": [
         {
             "class": "DockerRequirement",
-            "dockerPull": "python:2-slim"
+            "dockerPull": "python:3-slim"
         }
     ],
     "inputs": [