Add fallback for pkg-config in setup.py

setup.py

@@ -1,4 +1,3 @@
-import pathlib
 from setuptools import setup
 from Cython.Distutils.extension import Extension
 from Cython.Build import cythonize
@@ -9,32 +8,35 @@
 MOCKED_ENV = "PYPRECICE_MOCKED"
 
 
-def get_extensions():
+def find_precice():
     if not pkgconfig.exists("libprecice"):
-        raise Exception(
-            "\n".join(
-                [
-                    "pkg-config was unable to find libprecice.",
-                    "Please make sure that preCICE was installed correctly and pkg-config is able to find it.",
-                    "You may need to set PKG_CONFIG_PATH to include the location of the libprecice.pc file.",
-                    'Use "pkg-config --modversion libprecice" for debugging.',
-                ]
-            )
+        print(
+            "pkg-config was unable to find libprecice.\n"
+            "Please make sure that preCICE was installed correctly and pkg-config is able to find it.\n"
+            "You may need to set PKG_CONFIG_PATH to include the location of the libprecice.pc file.\n"
+            'Use "pkg-config --modversion libprecice" for debugging.'
         )
+        return [], ["-lprecice"]
+
+    version = pkgconfig.modversion("libprecice")
+    print(f"Found preCICE version {version}")
+    return pkgconfig.cflags("libprecice").split(), pkgconfig.libs("libprecice").split()
 
-    print("Found preCICE version " + pkgconfig.modversion("libprecice"))
+
+def get_extensions():
+    cflags, ldflags = find_precice()
 
     compile_args = ["-std=c++17"]
     link_args = []
     include_dirs = [numpy.get_include()]
     bindings_sources = ["cyprecice/cyprecice.pyx"]
-    compile_args += pkgconfig.cflags("libprecice").split()
+    compile_args += cflags
 
     if os.environ.get(MOCKED_ENV) is not None:
         print(f"Building mocked pyprecice as {MOCKED_ENV} is set")
         bindings_sources.append("test/Participant.cpp")
     else:
-        link_args += pkgconfig.libs("libprecice").split()
+        link_args += ldflags
 
     return [
         Extension(