Dumper: Fix failing GDB startup when using MinGW

Task-number: QTCREATORBUG-13892
Change-Id: Ia843cf4d88c574013e67cacaa8484b52fdbd4b8a
Reviewed-by: hjk <hjk@theqtcompany.com>

share/qtcreator/debugger/dumper.py

@@ -33,8 +33,13 @@ import struct
 import sys
 import base64
 import re
-import subprocess
 import time
+try:
+    import subprocess
+    hasSubprocess = True
+except:
+    hasSubprocess = False
+    hasPlot = False
 
 if sys.version_info[0] >= 3:
     xrange = range
@@ -78,18 +83,18 @@ SeparateUtf8StringFormat \
 # matplot based display for array-like structures.
 #
 try:
-    # FIXME: That might not be the one we want.
+    import matplotlib
-    pythonExecutable = sys.executable
-    subprocess.check_call([pythonExecutable, '-c', 'import matplotlib'])
     hasPlot = True
 except:
     hasPlot = False
 
-
+if hasSubprocess and hasPlot:
     matplotFigure = {}
     matplotCount = 0
 
     devNull = open(os.devnull)
+    # FIXME: That might not be the one we want.
+    pythonExecutable = sys.executable
     matplotProc = subprocess.Popen(args=[pythonExecutable, "-i"],
                 bufsize=0, stdin=subprocess.PIPE, stdout=devNull, stderr=devNull)