Update azure-pipelines-ci.yml for Azure Pipelines

azure-pipelines-ci.yml

@@ -34,12 +34,27 @@ stages:
       vmImage: 'ubuntu-latest'
     container: $[ variables['PythonMain'] ]
     steps:
+    - task: CacheBeta@0
+      inputs:
+        key: |
+          $(Build.SourcesDirectory)/requirements_test.txt
+          $(PythonMain)
+        path: $(Pipeline.Workspace)/venv.tar.gz
+        cacheHitVar: CacheRestored
     - script: |
+        set -e
         python -m venv venv
 
         . venv/bin/activate
         pip install -r requirements_test.txt
-      displayName: 'Setup Env'
+
+        tar -czf $(Pipeline.Workspace)/venv.tar.gz venv
+      displayName: 'Create Virtual Environment & Install Requirements'
+      condition: and(succeeded(), ne(variables['CacheRestored'], 'true'))
+    - script: |
+        tar -xzf $(Pipeline.Workspace)/venv.tar.gz
+      displayName: 'Restore Virtual Environment'
+      condition: and(succeeded(), eq(variables['CacheRestored'], 'true'))
     - script: |
         . venv/bin/activate
         flake8 homeassistant tests script
@@ -92,7 +107,7 @@ stages:
     - script: |
         set -e
         python -m venv venv
-        
+
         . venv/bin/activate
         pip install -U pip setuptools
         pip install -r requirements_test_all.txt -c homeassistant/package_constraints.txt