python: Avoid using 'is' to compare strings

This is the wrong operator to use, which only seems to work because
`os.name` and `'nt'` happen to be the same object. Python 3.8 also
produces a `SyntaxWarning` when encountering this pattern.

git-update

@@ -86,7 +86,7 @@ def update_repo(repo_name, repo_dir, revision, no_interaction, fetch_args=[], re
                   "\n=====================================" % (
                         out, repo_dir))
             try:
-                if os.name is 'nt':
+                if os.name == 'nt':
                     shell = os.environ.get("COMSPEC", r"C:\WINDOWS\system32\cmd.exe")
                 else:
                     shell = os.environ.get("SHELL", os.path.realpath("/bin/sh"))

gst-env.py

@@ -56,7 +56,7 @@ def prepend_env_var(env, var, value, sysroot):
     if value.startswith(sysroot):
         value = value[len(sysroot):]
     # Try not to exceed maximum length limits for env vars on Windows
-    if os.name is 'nt':
+    if os.name == 'nt':
         value = win32_get_short_path_name(value)
     env_val = env.get(var, '')
     val = os.pathsep + value + os.pathsep
@@ -144,7 +144,7 @@ def get_subprocess_env(options, gst_version):
     env["GST_PTP_HELPER"] = os.path.normpath(
         "%s/subprojects/gstreamer/libs/gst/helpers/gst-ptp-helper" % options.builddir)
 
-    if os.name is 'nt':
+    if os.name == 'nt':
         lib_path_envvar = 'PATH'
     elif platform.system() == 'Darwin':
         lib_path_envvar = 'DYLD_LIBRARY_PATH'
@@ -361,7 +361,7 @@ if __name__ == "__main__":
         gst_version += '-' + os.path.basename(options.wine)
 
     if not args:
-        if os.name is 'nt':
+        if os.name == 'nt':
             shell = get_windows_shell()
             if shell == 'powershell.exe':
                 args = ['powershell.exe']

scripts/common.py

@@ -11,7 +11,7 @@ import uuid
 ROOTDIR = os.path.abspath(os.path.dirname(__file__))
 
 
-if os.name is 'nt':
+if os.name == 'nt':
     import ctypes
     from ctypes import wintypes
     _GetShortPathNameW = ctypes.windll.kernel32.GetShortPathNameW