fix(ci): use absolute path for pip constraints

Author: gadomski

.github/workflows/tests.yml

@@ -26,6 +26,7 @@ jobs:
       NOXSESSION: ${{ matrix.session }}
       FORCE_COLOR: "1"
       PRE_COMMIT_COLOR: "always"
+      PIP_CONSTRAINTS: ${{ github.workspace }}/.github/workflows/constraints.txt
 
     steps:
       - name: Check out the repository
@@ -38,7 +39,7 @@ jobs:
 
       - name: Upgrade pip
         run: |
-          pip install --constraint=.github/workflows/constraints.txt pip
+          pip install --constraint=$PIP_CONSTRAINTS pip
           pip --version
 
       - name: Upgrade pip in virtual environments
@@ -52,13 +53,13 @@ jobs:
 
       - name: Install Poetry
         run: |
-          pipx install --pip-args=--constraint=.github/workflows/constraints.txt poetry
+          pipx install --pip-args=--constraint=$PIP_CONSTRAINTS poetry
           poetry --version
 
       - name: Install Nox
         run: |2
-          pipx install --pip-args=--constraint=.github/workflows/constraints.txt nox
-          pipx inject --pip-args=--constraint=.github/workflows/constraints.txt nox nox-poetry
+          pipx install --pip-args=--constraint=$PIP_CONSTRAINTS nox
+          pipx inject --pip-args=--constraint=$PIP_CONSTRAINTS nox nox-poetry
           nox --version
 
       - name: Compute pre-commit cache key
@@ -106,6 +107,8 @@ jobs:
   coverage:
     runs-on: ubuntu-latest
     needs: tests
+    env:
+      PIP_CONSTRAINTS: ${{ github.workspace }}/.github/workflows/constraints.txt
     steps:
       - name: Check out the repository
         uses: actions/checkout@v3
@@ -117,18 +120,18 @@ jobs:
 
       - name: Upgrade pip
         run: |
-          pip install --constraint=.github/workflows/constraints.txt pip
+          pip install --constraint=$PIP_CONSTRAINTS pip
           pip --version
 
       - name: Install Poetry
         run: |
-          pipx install --pip-args=--constraint=.github/workflows/constraints.txt poetry
+          pipx install --pip-args=--constraint=$PIP_CONSTRAINTS poetry
           poetry --version
 
       - name: Install Nox
         run: |
-          pipx install --pip-args=--constraint=.github/workflows/constraints.txt nox
-          pipx inject --pip-args=--constraint=.github/workflows/constraints.txt nox nox-poetry
+          pipx install --pip-args=--constraint=$PIP_CONSTRAINTS nox
+          pipx inject --pip-args=--constraint=$PIP_CONSTRAINTS nox nox-poetry
           nox --version
 
       - name: Download coverage data