Don't fail attach to pid if 'ProgramFiles' env var is not available. Fixes #1144

src/ptvsd/_vendored/pydevd/pydevd_attach_to_process/winappdbg/win32/dbghelp.py

@@ -47,29 +47,34 @@
 def _load_latest_dbghelp_dll():
 
     from os import getenv
-    from os.path import join
-
+    from os.path import join, exists
+
+    program_files_location = getenv("ProgramFiles")
+    if not program_files_location:
+        program_files_location = "C:\Program Files"
+
+    program_files_x86_location = getenv("ProgramFiles(x86)")
+
     if arch == ARCH_AMD64:
         if wow64:
             pathname = join(
-                            getenv("ProgramFiles(x86)",
-                                getenv("ProgramFiles")),
+                            program_files_x86_location or program_files_location,
                             "Debugging Tools for Windows (x86)",
                             "dbghelp.dll")
         else:
             pathname = join(
-                            getenv("ProgramFiles"),
+                            program_files_location,
                             "Debugging Tools for Windows (x64)",
                             "dbghelp.dll")
     elif arch == ARCH_I386:
         pathname = join(
-                        getenv("ProgramFiles"),
+                        program_files_location,
                         "Debugging Tools for Windows (x86)",
                         "dbghelp.dll")
     else:
         pathname = None
 
-    if pathname:
+    if pathname and exists(pathname):
         try:
             _dbghelp = ctypes.windll.LoadLibrary(pathname)
             ctypes.windll.dbghelp = _dbghelp