Attempt to fix coverity_scan build matrix in travis

.travis.yml

@@ -68,15 +68,32 @@ matrix:
             - libpcre2-dev
             - python3
             - python3-pip
-      coverity_scan:
-        project:
-          name: "fish-shell/fish-shell"
-          description: "The friendly interactive shell"
-        notification_email:
-          secure: "lq3AelSInSOqVJI2EZUTrsOrt9ev5c8DHMi7ESyefvv1p+7Qr2gRZmLa+dXLrkPegG+Op9Tykq9zwXRGC4pzC+0OelCKJgqpqkj6LwS8WSamiamAf9ZtPbANwSFMD17f/NTeG/OtBgq6Z87Nur2GEhxmSu3M9IEBOsnOgmCKo84="
-        build_command_prepend: "mkdir -p build; cd build; cmake -G Ninja -DCMAKE_CXX_COMPILER=clang++ .."
-        build_command: "ninja"
-        branch_pattern: coverity_scan_master
+    - os: linux
+      compiler: gcc
+      addons:
+        coverity_scan:
+          project:
+            name: "fish-shell/fish-shell"
+            description: "The friendly interactive shell"
+          notification_email: corydoras@ridiculousfish.com
+          build_command_prepend: "mkdir -p build; cd build; cmake -G Ninja .."
+          build_command: "ninja"
+          branch_pattern: coverity_scan_master
+        apt:
+          packages:
+            - expect
+            - gettext
+            - libncurses5-dev
+            - libpcre2-dev
+            - python3
+            - python3-pip
+      before_install:
+        - sudo pip3 install pexpect
+        - echo -n | openssl s_client -connect https://scan.coverity.com:443 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | sudo tee -a /etc/ssl/certs/ca-
+      env:
+          - secure: "Q1AS5iEi17s+xsRaMwfkxmm62UDaV47uE39pvXsNL+DO9YWbMMuhTpIOeYhxLvFNL3LMUFU2TwVpVRYX2YFGhNNaMSmjQfyQ+7q7/oSEo0aSqvQkwelpK/pwuRAXdv1MU4aQ6FrCEQ4VMO45WRo0o5WD26pvxjqRyAQ6ry+serA="
+          # Some warnings upgraded to errors to match Open Build Service platforms
+          - CXXFLAGS="-Werror=address -Werror=return-type"
     - os: osx
       before_install:
         - sudo pip3 install pexpect