Fail early in setup.py when clang can not be found

Previously only a warning was printed when clang could not be
found at setup.py time, resulting in a not very nice to parse
CMake error.

Make sure to fail early in setup.py if clang can not be found.

Also make sure to check that the clang source variable0 is not
"None", because passing "None" to run_process_output results
in an even more obscure Python error.

Change-Id: Ia94bf7da51996a3d9c74d5d9978b1bf9e26b03d5
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

2 files changed, 6 insertions, 5 deletions

diff --git a/setup.py b/setup.py
index e7553aacb..462913532 100644
--- a/setup.py
+++ b/setup.py
@@ -905,8 +905,8 @@ class pyside_build(_build):
                         clangBinDir, clangDir[1]))
                     additionalPaths.append(clangBinDir)
             else:
-                log.error("Failed to detect Clang by checking "
-                    "LLVM_INSTALL_DIR, CLANG_INSTALL_DIR, llvm-config")
+                raise DistutilsSetupError("Failed to detect Clang when checking "
+                                          "LLVM_INSTALL_DIR, CLANG_INSTALL_DIR, llvm-config")
 
         update_env_path(additionalPaths)
 
diff --git a/utils.py b/utils.py
index c80e6dd6c..11d9fbc64 100644
--- a/utils.py
+++ b/utils.py
@@ -775,9 +775,10 @@ def detectClang():
         if not clangDir:
             source = findLlvmConfig()
             try:
-                output = run_process_output([source, '--prefix'])
-                if output:
-                    clangDir = output[0]
+                if source is not None:
+                    output = run_process_output([source, '--prefix'])
+                    if output:
+                        clangDir = output[0]
             except OSError:
                 pass
     if clangDir: