Remove unused MesonException.get_msg_with_context()

After that, the only remaining user of get_error_location_string() is mlog,
so move that there.

mesonbuild/mesonlib.py

@@ -122,13 +122,6 @@ an_unpicklable_object = threading.Lock()
 class MesonException(Exception):
     '''Exceptions thrown by Meson'''
 
-    def get_msg_with_context(self):
-        s = ''
-        if hasattr(self, 'lineno') and hasattr(self, 'file'):
-            s = get_error_location_string(self.file, self.lineno) + ' '
-        s += str(self)
-        return s
-
 class EnvironmentException(MesonException):
     '''Exceptions thrown while processing and creating the build environment'''
 
@@ -1339,16 +1332,6 @@ def detect_subprojects(spdir_name, current_dir='', result=None):
                 result[basename] = [trial]
     return result
 
-# This isn't strictly correct. What we really want here is something like:
-# class StringProtocol(typing_extensions.Protocol):
-#
-#      def __str__(self) -> str: ...
-#
-# This would more accurately embody what this funcitonc an handle, but we
-# don't have that yet, so instead we'll do some casting to work around it
-def get_error_location_string(fname: str, lineno: str) -> str:
-    return '{}:{}:'.format(fname, lineno)
-
 def substring_is_in_list(substr: str, strlist: T.List[str]) -> bool:
     for s in strlist:
         if substr in s:

mesonbuild/mlog.py

@@ -221,9 +221,18 @@ def log_once(*args: T.Union[str, AnsiDecorator], is_error: bool = False,
     _logged_once.add(t)
     log(*args, is_error=is_error, **kwargs)
 
+# This isn't strictly correct. What we really want here is something like:
+# class StringProtocol(typing_extensions.Protocol):
+#
+#      def __str__(self) -> str: ...
+#
+# This would more accurately embody what this funcitonc an handle, but we
+# don't have that yet, so instead we'll do some casting to work around it
+def get_error_location_string(fname: str, lineno: str) -> str:
+    return '{}:{}:'.format(fname, lineno)
+
 def _log_error(severity: str, *rargs: T.Union[str, AnsiDecorator],
                once: bool = False, **kwargs: T.Any) -> None:
-    from .mesonlib import get_error_location_string
     from .environment import build_filename
     from .mesonlib import MesonException