Install VC for Python 2.7 only for py27-trial, only one that needs it

Author: nicoddemus

azure-pipelines.yml

@@ -4,6 +4,7 @@ trigger:
 
 variables:
   PYTEST_ADDOPTS: "--junitxml=build/test-results/$(tox.env).xml"
+  python.needs_vc: False
 
 jobs:
 
@@ -18,9 +19,13 @@ jobs:
       py27-xdist:
         python.version: '2.7'
         tox.env: 'py27-xdist'
-      py27-trial/numpy/nobyte:
+      py27-numpy/nobyte:
         python.version: '2.7'
-        tox.env: 'py27-trial,py27-numpy,py27-nobyte'
+        tox.env: 'py27-numpy,py27-nobyte'
+      py27-trial:
+        python.version: '2.7'
+        tox.env: 'py27-trial'
+        python.needs_vc: True
       py27-pluggymaster:
         python.version: '2.7'
         tox.env: 'pluggymaster'
@@ -60,7 +65,7 @@ jobs:
       architecture: 'x64'
 
   - script: choco install vcpython27
-    condition: eq(variables['python.version'], '2.7')
+    condition: eq(variables['python.needs_vc'], True)
     displayName: 'Install VC for py27'
 
   - script: python -m pip install --upgrade pip && pip install tox