Use workflow variables for tool versions in all workflows

Placement of this information at the top of the file, where it is easy to find and edit, facilitates updates to the
workflows as the tool version used for project development are bumped periodically.

This is an established convention in the "template" workflows, but I missed some applications of it. I think it's most
effective when done consistently throughout the workflows.

Author: per1234

.github/workflows/check-yaml-task.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/check-yaml-task.md
 name: Check YAML
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -65,7 +69,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

.github/workflows/spell-check-task.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/spell-check-task.md
 name: Spell Check
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -22,7 +26,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

workflow-templates/check-mkdocs-task.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/check-mkdocs-task.md
 name: Check Website
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -33,7 +37,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

workflow-templates/check-yaml-task.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/check-yaml-task.md
 name: Check YAML
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -65,7 +69,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

workflow-templates/dependabot/workflow-template-copies/.github/workflows/check-mkdocs-task.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/check-mkdocs-task.md
 name: Check Website
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -33,7 +37,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

workflow-templates/dependabot/workflow-template-copies/.github/workflows/check-yaml-task.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/check-yaml-task.md
 name: Check YAML
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -65,7 +69,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

workflow-templates/dependabot/workflow-template-copies/.github/workflows/deploy-cobra-mkdocs-versioned-poetry.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/deploy-cobra-mkdocs-versioned-poetry.md
 name: Deploy Website
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 on:
   push:
     branches:
@@ -52,7 +56,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: |

workflow-templates/dependabot/workflow-template-copies/.github/workflows/deploy-mkdocs-poetry.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/deploy-mkdocs-poetry.md
 name: Deploy Website
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -27,7 +31,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

workflow-templates/dependabot/workflow-template-copies/.github/workflows/deploy-mkdocs-versioned-poetry.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/deploy-mkdocs-versioned-poetry.md
 name: Deploy Website
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 on:
   push:
     branches:
@@ -47,7 +51,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: |

workflow-templates/dependabot/workflow-template-copies/.github/workflows/spell-check-task.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/spell-check-task.md
 name: Spell Check
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -22,7 +26,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

workflow-templates/deploy-cobra-mkdocs-versioned-poetry.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/deploy-cobra-mkdocs-versioned-poetry.md
 name: Deploy Website
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 on:
   push:
     branches:
@@ -52,7 +56,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: |

workflow-templates/deploy-mkdocs-poetry.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/deploy-mkdocs-poetry.md
 name: Deploy Website
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -27,7 +31,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry

workflow-templates/deploy-mkdocs-versioned-poetry.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/deploy-mkdocs-versioned-poetry.md
 name: Deploy Website
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 on:
   push:
     branches:
@@ -47,7 +51,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: |

workflow-templates/spell-check-task.yml

@@ -1,6 +1,10 @@
 # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/spell-check-task.md
 name: Spell Check
 
+env:
+  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  PYTHON_VERSION: "3.9"
+
 # See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows
 on:
   push:
@@ -22,7 +26,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: ${{ env.PYTHON_VERSION }}
 
       - name: Install Poetry
         run: pip install poetry