[gobject-introspection/fix.win.cmd.3-38] gicsanner/message.py: Windows: Fix running on different drives

[Chun-wei Fan <fanchunwei src gnome org>]

commit 95028675e877d7c4b2604f13113ac6b552f8b902
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Sep 18 15:06:36 2020 +0800

    gicsanner/message.py: Windows: Fix running on different drives
    
    os.path.relpath() will throw a ValueError when the two paths that
    are fed to it are on different drives, at least when running under
    cmd.exe consoles.
    
    Fix this by falling back to the full path when this ValueError is
    thrown.

 giscanner/message.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/giscanner/message.py b/giscanner/message.py
index 9057c23c1..24f1b7dfe 100644
--- a/giscanner/message.py
+++ b/giscanner/message.py
@@ -75,8 +75,14 @@ class Position(object):
                                         self.column or -1)
 
     def format(self, cwd):
-        filename = os.path.relpath(os.path.realpath(self.filename),
-                                   os.path.realpath(cwd))
+        # Windows: We may be using different drives self.filename and cwd,
+        #          which leads to a ValuError when using os.path.relpath().
+        #          In that case, just use the entire path of self.filename
+        try:
+            filename = os.path.relpath(os.path.realpath(self.filename),
+                                       os.path.realpath(cwd))
+        except ValueError:
+            filename = os.path.realpath(self.filename)
 
         if self.column is not None:
             return '%s:%d:%d' % (filename, self.line, self.column)