Address Python API CI build errors

library/cpp/CMakeLists.txt

@@ -28,6 +28,10 @@ if (GENERATE_WAVEMAP_INSTALL_RULES
       "Disabling option to install. Not all dependencies are system libraries.")
   set(GENERATE_WAVEMAP_INSTALL_RULES OFF)
 endif ()
+# Always install the library if it's being built as part of a Python package
+if (SKBUILD)
+  set(GENERATE_WAVEMAP_INSTALL_RULES ON)
+endif ()
 
 # Libraries
 add_subdirectory(src/core)

library/python/CMakeLists.txt

@@ -28,22 +28,14 @@ endif ()
 # Load the wavemap library (if not already loaded)
 if (NOT TARGET wavemap::wavemap_core)
   if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/../cpp/)
-    message(STATUS "Loading wavemap library installed on system")
+    message(STATUS "Loading wavemap C++ library sources")
     add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/../cpp
         ${CMAKE_CURRENT_BINARY_DIR}/wavemap)
   else ()
-    set(WAVEMAP_VERSION main)
-    message(STATUS
-        "Loading wavemap library from GitHub (ref ${WAVEMAP_VERSION})")
-    cmake_minimum_required(VERSION 3.18)
-    include(FetchContent)
-    FetchContent_Declare(
-        ext_wavemap PREFIX wavemap
-        GIT_REPOSITORY https://github.com/ethz-asl/wavemap.git
-        GIT_TAG ${WAVEMAP_VERSION}
-        GIT_SHALLOW 1
-        SOURCE_SUBDIR library/cpp)
-    FetchContent_MakeAvailable(ext_wavemap)
+    message(ERROR
+        "Can not load wavemap C++ library sources. Are you using an old "
+        "version of pip? If so, retry after upgrading with "
+        "\"python3 -m pip install --upgrade pip\".")
   endif ()
 endif ()