Index: lldb/trunk/packages/Python/lldbsuite/test/configuration.py
===================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/configuration.py
+++ lldb/trunk/packages/Python/lldbsuite/test/configuration.py
@@ -188,5 +188,5 @@
     """
     Get the path to the FileCheck testing tool.
     """
-    assert os.path.lexists(filecheck)
-    return filecheck
+    if os.path.lexists(filecheck):
+        return filecheck
Index: lldb/trunk/packages/Python/lldbsuite/test/dotest.py
===================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/dotest.py
+++ lldb/trunk/packages/Python/lldbsuite/test/dotest.py
@@ -308,11 +308,15 @@
           'xcrun -find -toolchain default dsymutil')
 
     if args.filecheck:
-        # The CMake build passes in a path to a working FileCheck binary.
+        # The lldb-dotest script produced by the CMake build passes in a path
+        # to a working FileCheck binary. So does one specific Xcode project
+        # target. However, when invoking dotest.py directly, a valid --filecheck
+        # option needs to be given.
         configuration.filecheck = os.path.abspath(args.filecheck)
-    else:
-        logging.error('No valid FileCheck executable; aborting...')
-        sys.exit(-1)
+
+    if not configuration.get_filecheck_path():
+        logging.warning('No valid FileCheck executable; some tests may fail...')
+        logging.warning('(Double-check the --filecheck argument to dotest.py)')
 
     if args.channels:
         lldbtest_config.channels = args.channels
Index: lldb/trunk/packages/Python/lldbsuite/test/lldbtest.py
===================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/lldbtest.py
+++ lldb/trunk/packages/Python/lldbsuite/test/lldbtest.py
@@ -2237,6 +2237,8 @@
 
         # Run FileCheck.
         filecheck_bin = configuration.get_filecheck_path()
+        if not filecheck_bin:
+            self.assertTrue(False, "No valid FileCheck executable specified")
         filecheck_args = [filecheck_bin, check_file_abs]
         if filecheck_options:
             filecheck_args.append(filecheck_options)