Install from sdist in CI (#4335)

* Update azure-pipelines.yml

* Update azure-pipelines.yml

* Update azure-pipelines.yml

* Update azure-pipelines.yml

* Update azure-pipelines.yml

* Update azure-pipelines.yml

azure-pipelines.yml

@@ -79,14 +79,24 @@ jobs:
   # Downgrading pip is necessary to prevent a wheel version incompatiblity.
   # Might be fixed in the future or some other way, so investigate again.
   - script: |
-      python -m pip install --upgrade pip==18.1
+      python -m pip install -U pip==18.1 setuptools
       pip install -r requirements.txt
     displayName: 'Install dependencies'
 
   - script: |
       python setup.py build_ext --inplace
-      pip install -e .
-    displayName: 'Build and install'
+      python setup.py sdist --formats=gztar
+    displayName: 'Compile and build sdist'
+
+  - task: DeleteFiles@1
+    inputs:
+      contents: 'spacy'
+    displayName: 'Delete source directory'
+
+  - bash: |
+      SDIST=$(python -c "import os;print(os.listdir('./dist')[-1])" 2>&1)
+      pip install dist/$SDIST
+    displayName: 'Install from sdist'
 
   - script: python -m pytest tests
     displayName: 'Run tests'