Try some os x tests on travis again.

.travis.yml

@@ -106,23 +106,23 @@ matrix:
         - dlib/travis/build-and-test.sh
 
     ###################
-    # # Disabled because travis's OS X machines take hours (or days) to begin
-    # running.  Or maybe they are just broken entirely.  Who knows.
-    #- language: cpp
-    #  os: osx
-    #  osx_image: xcode9.2
-    #  env:
-    #    - VARIANT=test
-    #  script:
-    #    - dlib/travis/build-and-test.sh
-         
+    - language: cpp
+      os: osx
+      osx_image: xcode9.2
+      env:
+        - VARIANT=test
+        # Don't test the timer because it relies on the machine running it not
+        # being under high load, but that seems to be unlikely on the travis
+        # osx VMs.
+        - DISABLED_TESTS="--no_test_timer"
+      script:
+        - dlib/travis/build-and-test.sh
 
     ###################
-    #- language: python
-    #  os: osx
-    #  osx_image: xcode9.2
-    #  python: 3.5
-    #  env:
-    #    - VARIANT=python-api
-    #  script:
-    #    - dlib/travis/build-and-test.sh
+    - language: cpp
+      os: osx
+      osx_image: xcode9.2
+      env:
+        - VARIANT=python-api
+      script:
+        - dlib/travis/build-and-test.sh

dlib/travis/build-and-test.sh

@@ -13,7 +13,7 @@ if [ "$VARIANT" = "test" ]; then
   cd build
   cmake ../dlib/test 
   cmake --build . --target dtest -- -j 2
-  ./dtest --runall
+  ./dtest --runall $DISABLED_TESTS
 fi
 
 # build dlib and tests
@@ -22,7 +22,7 @@ if [ "$VARIANT" = "test-debug" ]; then
   cd build
   cmake ../dlib/test -DDLIB_ENABLE_ASSERTS=1
   cmake --build . --target dtest -- -j 2
-  ./dtest --runall
+  ./dtest --runall $DISABLED_TESTS
 fi
 
 if [ "$VARIANT" = "dlib_all_source_cpp" ]; then