The file doesn't exist in the current working directory. The user is asking me to generate a patch based on the issue description. Based on the hints provided in the issue, I can generate the patch directly.

Let me produce the patch based on the information provided:

--- a/sympy/matrices/expressions/blockmatrix.py
+++ b/sympy/matrices/expressions/blockmatrix.py
@@ -301,7 +301,7 @@ def blocks(self):
         data = [[mats[i] if i == j else ZeroMatrix(mats[i].rows, mats[j].cols)
                         for j in range(len(mats))]
                         for i in range(len(mats))]
-        return ImmutableDenseMatrix(data)
+        return ImmutableDenseMatrix(data, evaluate=False)
 
     @property
     def shape(self):