Fixed 3.6 and added 3.9

.travis.yml

@@ -18,23 +18,41 @@ install:
 # - pip install pytest-faulthandler
   - pip install PyVirtualDisplay
   - pip install pytest-xvfb
-  - pip install pytest-cov
   - pip install pytest-qt
-  - pip install codecov
 
 stages:
-  - name: Initial
-  - name: Full
+  - name: Main
+  - name: Supported
 
 jobs:
   include:
-    - stage: Initial
-      python: 3.8
-      script: python -m pytest --cov=nw -m "project|core|gui" -v
-      after_success: codecov
-      after_failure: cat /sys/fs/cgroup/memory/memory.max_usage_in_bytes
+    - stage:
+      - Main
+      python:
+      - 3.8
+      install:
+      - pip install pytest-cov
+      - pip install codecov
+      script:
+      - python -m pytest --cov=nw -m "project|core|gui" -v
+      after_success:
+      - codecov
+      after_failure:
+      - cat /sys/fs/cgroup/memory/memory.max_usage_in_bytes
 
-    - stage: Full
-      python: 3.6
-    - python: 3.7
-      script: python -m pytest -m "project|core|gui" -v
+    - stage:
+      - Supported
+      python:
+      - 3.6
+      script:
+      - python -m pytest -m "project|core|gui" -v
+
+    - python:
+      - 3.7
+      script:
+      - python -m pytest -m "project|core|gui" -v
+
+    - python:
+      - 3.9-dev
+      script:
+      - python -m pytest -m "project|core|gui" -v