Avoid temprary variable assignment by returning value directly from try

block.

IPython/lib/latextools.py

@@ -143,10 +143,9 b' def latex_to_png_dvipng(s, wrap):'
                 stdout=devnull, stderr=devnull)
 
         with open(outfile, "rb") as f:
-            bin_data = f.read()
+            return f.read()
     finally:
         shutil.rmtree(workdir)
-    return bin_data
 
 
 def kpsewhich(filename):