bugfix: don't crash when c++filt is not available in the toolchain

The PIC xc16 toolchain does not include any c++ tools and puncover crashed while trying to open the elf file. This fixes it.

puncover/gcc_tools.py

@@ -20,7 +20,8 @@ def gcc_tool_path(self, name):
         return path
 
     def gcc_tool_lines(self, name, args, cwd=None):
-        proc = subprocess.Popen([self.gcc_tool_path(name)] + args, stdout=subprocess.PIPE, cwd=cwd)
+        proc = subprocess.Popen(
+            [self.gcc_tool_path(name)] + args, stdout=subprocess.PIPE, cwd=cwd)
         return proc.stdout.readlines()
 
     def get_assembly_lines(self, elf_file):
@@ -41,7 +42,12 @@ def chunks(l):
             for i in range(0, len(l), chunk_size):
                 yield l[i:i + chunk_size]
 
-        lines_list =  [self.gcc_tool_lines('c++filt', c) for c in chunks(symbol_names)]
+        lines_list = [c for c in chunks(symbol_names)]
+        try:
+            lines_list = [self.gcc_tool_lines(
+                'c++filt', c) for c in chunks(symbol_names)]
+        except Exception as e:
+            print("Unable to demangle C++ symbol names: {}".format(e))
         lines = list(itertools.chain.from_iterable(lines_list))
         demangled = list(s.rstrip() for s in lines)