Print ERROR: infront of {NonBug,BuildFailed}Error (MR 2298)

Make the handling of the custom NonBugError and BuildFailedError
exceptions more consistent with the handling of other exceptions, by
printing "ERROR: " infront of the actual error text. Then we don't need
to duplicate that where we raise the errors. pmbootstrap prints "ERROR"
in red.

pmb/__init__.py

@@ -88,11 +88,11 @@ def main():
         sys.exit(130)  # SIGINT(2) + 128
 
     except NonBugError as exception:
-        logging.error(exception)
+        logging.error(f"ERROR: {exception}")
         return 2
 
     except BuildFailedError as exception:
-        logging.error(exception)
+        logging.error(f"ERROR: {exception}")
         print_log_hint(args)
         return 3
 

pmb/build/_package.py

@@ -535,6 +535,6 @@ def package(args, pkgname, arch=None, force=False, strict=False,
         (output, cmd, env) = run_abuild(args, apkbuild, arch, strict, force, cross,
                                         suffix, src, bootstrap_stage)
     except RuntimeError:
-        raise BuildFailedError(f"ERROR: Build for {arch}/{pkgname} failed!")
+        raise BuildFailedError(f"Build for {arch}/{pkgname} failed!")
     finish(args, apkbuild, arch, output, strict, suffix)
     return output

pmb/parse/kconfig.py

@@ -272,7 +272,7 @@ def check(args, pkgname, components_list=[], details=False, must_exist=True):
         config_name_split = config_name.split(".")
 
         if len(config_name_split) != 2:
-            raise NonBugError(f"ERROR: {config_name} is not a valid kernel config "
+            raise NonBugError(f"{config_name} is not a valid kernel config"
                               "name. Ensure that the _config property in your "
                               "kernel APKBUILD has a . before the "
                               "architecture name, e.g. .aarch64 or .armv7, "