reformat some warnings for better code readability

mesonbuild/compilers/cpp.py

@@ -58,7 +58,7 @@ def non_msvc_eh_options(eh: str, args: T.List[str]) -> None:
     if eh == 'none':
         args.append('-fno-exceptions')
     elif eh in {'s', 'c'}:
-        mlog.warning('non-MSVC compilers do not support ' + eh + ' exception handling.' +
+        mlog.warning(f'non-MSVC compilers do not support {eh} exception handling. '
                      'You may want to set eh to \'default\'.')
 
 class CPPCompiler(CLikeCompiler, Compiler):

mesonbuild/interpreter/interpreter.py

@@ -2905,10 +2905,12 @@ class Interpreter(InterpreterBase, HoldableObject):
             return
         if (self.coredata.options[OptionKey('b_lundef')].value and
                 self.coredata.options[OptionKey('b_sanitize')].value != 'none'):
-            mlog.warning('''Trying to use {} sanitizer on Clang with b_lundef.
-This will probably not work.
-Try setting b_lundef to false instead.'''.format(self.coredata.options[OptionKey('b_sanitize')].value),
-                         location=self.current_node)
+            value = self.coredata.options[OptionKey('b_sanitize')].value
+            mlog.warning(textwrap.dedent(f'''\
+                    Trying to use {value} sanitizer on Clang with b_lundef.
+                    This will probably not work.
+                    Try setting b_lundef to false instead.'''),
+                location=self.current_node)  # noqa: E128
 
     # Check that the indicated file is within the same subproject
     # as we currently are. This is to stop people doing