Better diagnostics for non-working cygdb installations. (GH-3489)

If your installation is faulty, cygdb will now print the filepath of the code that caused an exception, and the path of the python interpreter will be printed for better debugging.

Cython/Debugger/Cygdb.py

@@ -45,6 +45,7 @@ def make_command_file(path_to_debug_info, prefix_code='', no_import=False):
             set print pretty on
 
             python
+            try:
                 # Activate virtualenv, if we were launched from one
                 import os
                 virtualenv = os.getenv('VIRTUAL_ENV')
@@ -54,8 +55,13 @@ def make_command_file(path_to_debug_info, prefix_code='', no_import=False):
                         virtualenv, path_to_activate_this_py))
                     with open(path_to_activate_this_py) as f:
                         exec(f.read(), dict(__file__=path_to_activate_this_py))
-
                 from Cython.Debugger import libcython, libpython
+            except Exception as ex:
+                from traceback import print_exc
+                print("There was an error in Python code originating from the file ''' + str(__file__) + '''")
+                print("It used the Python interpreter " + str(sys.executable))
+                print_exc()
+                exit(1)
             end
             '''))
 
@@ -79,8 +85,8 @@ def make_command_file(path_to_debug_info, prefix_code='', no_import=False):
                     gdb.lookup_type('PyModuleObject')
                 except RuntimeError:
                     sys.stderr.write(
-                        'Python was not compiled with debug symbols (or it was '
-                        'stripped). Some functionality may not work (properly).\\n')
+                        "''' + interpreter + ''' was not compiled with debug symbols (or it was "
+                        "stripped). Some functionality may not work (properly).\\n")
                 end
 
                 source .cygdbinit