Regenerate .travis.yml

This commit was performed automatically by a script.
https://github.com/RyanGlScott/travis-maintenance

Author: RyanGlScott

.travis.yml

@@ -36,9 +36,9 @@ before_cache:
 
 matrix:
   include:
-    - compiler: "ghc-8.6.2"
+    - compiler: "ghc-8.6.3"
     # env: TEST=--disable-tests BENCH=--disable-benchmarks
-      addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-8.6.2], sources: [hvr-ghc]}}
+      addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-8.6.3], sources: [hvr-ghc]}}
     - compiler: "ghc-8.4.4"
     # env: TEST=--disable-tests BENCH=--disable-benchmarks
       addons: {apt: {packages: [ghc-ppa-tools,cabal-install-2.4,ghc-8.4.4], sources: [hvr-ghc]}}
@@ -115,6 +115,7 @@ install:
     fi
   - grep -Ev -- '^\s*--' ${HOME}/.cabal/config | grep -Ev '^\s*$'
   - "printf 'packages: \".\"\\n' > cabal.project"
+  - "printf 'write-ghc-environment-files: always\\n' >> cabal.project"
   - touch cabal.project.local
   - "if ! $NOINSTALLEDCONSTRAINTS; then for pkg in $($HCPKG list --simple-output); do echo $pkg  | grep -vw -- mtl | sed 's/^/constraints: /' | sed 's/-[^-]*$/ installed/' >> cabal.project.local; done; fi"
   - cat cabal.project || true
@@ -136,6 +137,7 @@ script:
   - cd ${DISTDIR} || false
   - find . -maxdepth 1 -name '*.tar.gz' -exec tar -xvf '{}' \;
   - "printf 'packages: mtl-*/*.cabal\\n' > cabal.project"
+  - "printf 'write-ghc-environment-files: always\\n' >> cabal.project"
   - touch cabal.project.local
   - "if ! $NOINSTALLEDCONSTRAINTS; then for pkg in $($HCPKG list --simple-output); do echo $pkg  | grep -vw -- mtl | sed 's/^/constraints: /' | sed 's/-[^-]*$/ installed/' >> cabal.project.local; done; fi"
   - cat cabal.project || true

mtl.cabal

@@ -25,7 +25,7 @@ tested-with:
   GHC==8.0.2,
   GHC==8.2.2,
   GHC==8.4.4,
-  GHC==8.6.2
+  GHC==8.6.3
 
 source-repository head
   type: git