Travis: use the in-tree Python package requirements

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/.travis.yml b/.travis.yml
index 56e1456..3354607 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,7 +19,7 @@
       language: python # Needed to get pip for Python 3
       python: 3.5 # version from Ubuntu 16.04
       install:
-        - pip install mypy==0.780 pylint==2.4.4
+        - scripts/min_requirements.py
       script:
         - tests/scripts/all.sh -k 'check_*'
         - tests/scripts/all.sh -k test_default_out_of_box