.travis.yml: test notebook conversion with GHC 8.6 (#1102)

* .travis.yml: test notebook conversion with GHC 8.6

* test/acceptance.nbconvert.sh: ignore different line numbers for HLint

.travis.yml

@@ -234,7 +234,7 @@ matrix:
               stack exec -- ihaskell install --stack
               test/acceptance.nbconvert.sh stack exec -- jupyter nbconvert
           fi
-    - env: DISPLAY=false   USE_STACK_YAML="stack.yaml"     # GHC 8.6.5
+    - env: DISPLAY=true   USE_STACK_YAML="stack.yaml"     # GHC 8.6.5
       language: python
       dist: xenial
       # Test against different stack LTS versions.

test/acceptance.nbconvert.sh

@@ -29,5 +29,5 @@ set -euo pipefail
 
 $* --to=notebook --execute --allow-errors --stdout test/acceptance.nbconvert.in.ipynb > test/acceptance.nbconvert.out.ipynb
 
-diff <(grep -v 'version' test/acceptance.nbconvert.in.ipynb) <(grep -v 'version' test/acceptance.nbconvert.out.ipynb)
+diff <(grep -v -e 'version' -e 'Line ' test/acceptance.nbconvert.in.ipynb) <(grep -v -e 'version' -e 'Line ' test/acceptance.nbconvert.out.ipynb)