Install Poetry using pipx in CI workflow

nox-poetry crashed in the GA workflow when parsing requirements with packaging < 21.1 and pyparsing >= 3

See pypa/packaging#482 for the upstream discussion.

.github/workflows/ci.yml

@@ -40,12 +40,13 @@ jobs:
 
       - name: Install Poetry
         run: |
-          pip install --constraint=.github/workflows/constraints.txt poetry
+          pipx install --pip-args=--constraint=.github/workflows/constraints.txt poetry
           poetry --version
 
       - name: Install Nox
         run: |
-          pip install --constraint=.github/workflows/constraints.txt nox nox-poetry
+          pipx install --pip-args=--constraint=.github/workflows/constraints.txt nox
+          pipx inject --pip-args=--constraint=.github/workflows/constraints.txt nox nox-poetry
           nox --version
 
       - name: Install PyTables dependencies
@@ -121,12 +122,13 @@ jobs:
 
       - name: Install Poetry
         run: |
-          pip install --constraint=.github/workflows/constraints.txt poetry
+          pipx install --pip-args=--constraint=.github/workflows/constraints.txt poetry
           poetry --version
 
       - name: Install Nox
         run: |
-          pip install --constraint=.github/workflows/constraints.txt nox nox-poetry
+          pipx install --pip-args=--constraint=.github/workflows/constraints.txt nox
+          pipx inject --pip-args=--constraint=.github/workflows/constraints.txt nox nox-poetry
           nox --version
 
       - name: Download coverage data