Extract function for launching httpbin into its own file

Allow reusing it between GitHub and Travis CI.

Also show httpbin log in Travis CI logs too, not just on GitHub.

.github/workflows/ci.yml

@@ -189,13 +189,9 @@ jobs:
         if: matrix.skip_testing != true
         working-directory: tests
         run: |
-          echo "Launching httpbin"
-          # Current decorator (>= 5) is incompatible with Python 2 which we
-          # still use under in some builds, so explicitly use a version which
-          # is known to work.
-          pip install decorator==4.4.2 httpbin
-          python -m httpbin.core 2>&1 >httpbin.log &
-          export WX_TEST_WEBREQUEST_URL=http://localhost:5000
+          . ../build/tools/httpbin.sh
+
+          httpbin_launch
 
           export ASAN_OPTIONS=fast_unwind_on_malloc=0
 
@@ -210,11 +206,9 @@ jobs:
                 ./test || rc=$?
             fi
           fi
+
           if [ -n "$rc" ]; then
-            echo '*** Tests failed, contents of httpbin.log follows: ***'
-            echo '-----------------------------------------------------------'
-            cat httpbin.log
-            echo '-----------------------------------------------------------'
+            httpbin_show_log
             exit $rc
           fi