BLD: add found Cython version to check in cythonize.py

Ref gh-18138, which has a confusing situation where the
correct version seems installed but this check still raises.

1 files changed, 4 insertions, 1 deletions

diff --git a/tools/cythonize.py b/tools/cythonize.py
index 6cebf0f72..911b81243 100755
--- a/tools/cythonize.py
+++ b/tools/cythonize.py
@@ -56,6 +56,7 @@ def process_pyx(fromfile, tofile):
 
     try:
         # try the cython in the installed python first (somewhat related to scipy/scipy#2397)
+        import Cython
         from Cython.Compiler.Version import version as cython_version
     except ImportError:
         # The `cython` command need not point to the version installed in the
@@ -73,7 +74,9 @@ def process_pyx(fromfile, tofile):
         required_version = LooseVersion('0.29.21')
 
         if LooseVersion(cython_version) < required_version:
-            raise RuntimeError(f'Building {VENDOR} requires Cython >= {required_version}')
+            cython_path = Cython.__file__
+            raise RuntimeError(f'Building {VENDOR} requires Cython >= {required_version}'
+                               f', found {cython_version} at {cython_path}')
         subprocess.check_call(
             [sys.executable, '-m', 'cython'] + flags + ["-o", tofile, fromfile])