Fix travis ci

Author: Taaku18

.travis.yml

@@ -8,13 +8,13 @@ matrix:
     name: "Python 3.6.7 on Xenial Linux"
   - name: "Python 3.7.4 on macOS"
     os: osx
-    osx_image: xcode11
+    osx_image: xcode11.2
     language: shell
-  - name: "Python 3.7.4 on Windows"
+  - name: "Python 3.7.5 on Windows"
     os: windows
     language: shell
     before_install:
-      - choco install python
+      - choco install python --version=3.7.5
       - python -m pip install --upgrade pip
     env: PATH=/c/Python37:/c/Python37/Scripts:$PATH