[dotest] Add logging to investigate CI issue.

We're seeing an odd issue on GreenDragon's lldb-cmake-matrix. Dotest is
unable to move a log file (OSError: [Errno 2] No such file or
directory). The os.rename call is guarded with a check that the source
file and destination directory exist.

This wraps the call in a try-except that prints the source and
destination path to see which component seemingly doesn't exist.

llvm-svn: 351611

lldb/packages/Python/lldbsuite/test/lldbtest.py

@@ -1228,7 +1228,12 @@ class Base(unittest2.TestCase):
                         remove_file(dst)
 
                     lldbutil.mkdir_p(os.path.dirname(dst))
-                    os.rename(src, dst)
+                    try:
+                        os.rename(src, dst)
+                    except OSError:
+                        print("src (exists={}): {}".format(os.path.exists(src), src))
+                        print("dst (exists={}): {}".format(os.path.exists(dst), dst))
+                        raise
         else:
             # success!  (and we don't want log files) delete log files
             for log_file in log_files_for_this_test: