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 39ae19c..f910ace 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,8 +18,6 @@
           - libc6-dev-armel-cross
       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
       script:
         - tests/scripts/all.sh -k 'check_*'
         - tests/scripts/all.sh -k test_default_out_of_box
@@ -53,6 +51,9 @@
     - SEED=1
     - secure: "FrI5d2s+ckckC17T66c8jm2jV6i2DkBPU5nyWzwbedjmEBeocREfQLd/x8yKpPzLDz7ghOvr+/GQvsPPn0dVkGlNzm3Q+hGHc/ujnASuUtGrcuMM+0ALnJ3k4rFr9xEvjJeWb4SmhJO5UCAZYvTItW4k7+bj9L+R6lt3TzQbXzg="
 
+install:
+  - scripts/min_requirements.py
+
 addons:
   apt:
     packages: