Disable networking before installing local package

Workaround-For: PyO3/maturin#1971

.github/workflows/maturin.yml

@@ -8,6 +8,8 @@
 # * remove the "Upload to GitHub release" step
 # * remove the emscripten / pytest step -- this fails for reasons that are too
 #   hard to to debug right now
+# * added --no-index to local package installation as
+#   workaround for https://github.com/PyO3/maturin/issues/1971
 #
 name: CI
 
@@ -64,7 +66,7 @@ jobs:
         shell: bash
         run: |
           set -e
-          pip install cbor-diag --find-links dist --force-reinstall
+          pip install cbor-diag --no-index --find-links dist --force-reinstall
           pip install pytest
           pytest
       - name: pytest
@@ -80,7 +82,7 @@ jobs:
             pip3 install -U pip pytest
           run: |
             set -e
-            pip3 install cbor-diag --find-links dist --force-reinstall
+            pip3 install cbor-diag --no-index --find-links dist --force-reinstall
             pytest
 
   windows:
@@ -114,7 +116,7 @@ jobs:
         shell: bash
         run: |
           set -e
-          pip install cbor-diag --find-links dist --force-reinstall
+          pip install cbor-diag --no-index --find-links dist --force-reinstall
           pip install pytest
           pytest
 
@@ -148,7 +150,7 @@ jobs:
         shell: bash
         run: |
           set -e
-          pip install cbor-diag --find-links dist --force-reinstall
+          pip install cbor-diag --no-index --find-links dist --force-reinstall
           pip install pytest
           pytest