travis fixups

make travis execute py3.7 again

modernise config

.travis.yml

@@ -1,3 +1,6 @@
+dist: trusty
+sudo: false
+cache: pip
 language: python
 
 # whitelist branches on which tests will be run
@@ -14,20 +17,8 @@ addons:
     - swig
     # needed for GMPY
     - libgmp-dev
-
-python:
-  - 2.6
-  - 2.7
-  - 3.3
-  - 3.4
-  - 3.5
-  - 3.6
-  - 3.7
-
-# workaround for 3.7 not available in default configuration
-# travis-ci/travis-ci#9815
-dist: trusty
-sudo: false
+before_cache:
+  - rm -f $HOME/.cache/pip/log/debug.log
 
 env:
   - TACKPY=true
@@ -40,6 +31,8 @@ matrix:
 # travis-ci/travis-ci#9815
     - python: 3.7
   include:
+    - python: 2.6
+      env: TACKPY=false
     - python: 2.7
       env: TACKPY=true
     - python: 3.4
@@ -56,7 +49,6 @@ matrix:
 # travis-ci/travis-ci#9815
     - python: 3.7
       dist: xenial
-      sudo: true
       env: M2CRYPTO=true
     - python: 2.7
       env: PYCRYPTO=true
@@ -68,7 +60,6 @@ matrix:
       env: PYCRYPTO=true
     - python: 3.7
       dist: xenial
-      sudo: true
       env: PYCRYPTO=true
     - python: 2.7
       env: GMPY=true
@@ -80,7 +71,6 @@ matrix:
       env: GMPY=true
     - python: 3.7
       dist: xenial
-      sudo: true
       env: GMPY=true
     - python: 2.7
       env: M2CRYPTO=true PYCRYPTO=true GMPY=true
@@ -92,7 +82,6 @@ matrix:
       env: M2CRYPTO=true PYCRYPTO=true GMPY=true
     - python: 3.7
       dist: xenial
-      sudo: true
       env: M2CRYPTO=true PYCRYPTO=true GMPY=true CC_COV=true
 
 before_install:
@@ -163,8 +152,6 @@ script:
         done
       fi
 
-sudo: false
-
 after_success:
  - travis_retry coveralls
  - if [[ $CC_COV == 'true' ]]; then coverage xml; ./cc-test-reporter after-build --exit-code $TRAVIS_TEST_RESULT; fi