benchtests: Avoid a display error when running in text terminal

The compare_strings.py script generates a graph for the benchmarks it
performs a comparison on and that fails if X is not available.  Avoid
the error and ensure that only the graph is generated and saved as a
PNG file.

	* benchtests/scripts/compare_strings.py: Avoid display error
	when generating graph.

1 files changed, 2 insertions, 0 deletions

diff --git a/benchtests/scripts/compare_strings.py b/benchtests/scripts/compare_strings.py
index 43e70ebee2..b3c57e2b34 100755
--- a/benchtests/scripts/compare_strings.py
+++ b/benchtests/scripts/compare_strings.py
@@ -21,6 +21,8 @@ Given a string benchmark result file, print a table with comparisons with a
 baseline.  The baseline is the first function, which typically is the builtin
 function.
 """
+import matplotlib as mpl
+mpl.use('Agg')
 
 import sys
 import os