build: remove the tfpwa dependency explicitly, as it's not on pypi

.github/workflows/ci.yml

@@ -49,7 +49,7 @@ jobs:
         run: |
           which python
           python -V
-          uv pip install -e ".[dev]"
+          uv pip install -e ".[dev]" tfpwa@git+https://github.com/jiangyi15/tf-pwa
           uv pip install zfit@git+https://github.com/zfit/zfit
       - name: Test with pytest
         run: |

pyproject.toml

@@ -37,7 +37,6 @@ dynamic = ["version"]
 
 [project.optional-dependencies]
 
-tfpwa = ["tfpwa@git+https://github.com/jiangyi15/tf-pwa"]
 compwa = [
     "qrules",
     "ampform",
@@ -46,7 +45,7 @@ compwa = [
 pyhf = [
     "pyhf",
 ]
-all = ["zfit-physics[tfpwa,pyhf,compwa]"]
+all = ["zfit-physics[pyhf,compwa]"]
 test = [
     "pytest",
     "pytest-cov",

src/zfit_physics/tfpwa/__init__.py

@@ -1,3 +1,7 @@
+try:
+    import tf_pwa
+except ImportError:
+    raise ImportError("tf-pwa is required to use zfit-physics-tfpwa. This can currently only be installed from source, i.e. via `pip install git+https://github.com/jiangyi15/tf-pwa`")
 from . import loss, variables
 
 __all__ = ["loss", "variables"]