makemessages: Fix handling of handlebars whitespace control.

Our logic for extracting strings from templates did not properly
handle the syntax for code containing whitespace control characters,
resulting in a couple strings from subscribe_to_more_streams.hbs not
being processed.

zerver/management/commands/makemessages.py

@@ -52,9 +52,9 @@ strip_whitespace_left = re.compile(
 )
 
 regexes = [
-    r"{{#tr}}([\s\S]*?)(?:{{/tr}}|{{#\*inline )",  # '.' doesn't match '\n' by default
-    r'{{\s*t "([\s\S]*?)"\W*}}',
-    r"{{\s*t '([\s\S]*?)'\W*}}",
+    r"{{~?#tr}}([\s\S]*?)(?:~?{{/tr}}|{{#\*inline )",  # '.' doesn't match '\n' by default
+    r'{{~?\s*t "([\s\S]*?)"\W*~?}}',
+    r"{{~?\s*t '([\s\S]*?)'\W*~?}}",
     r'\(t "([\s\S]*?)"\)',
     r'=\(t "([\s\S]*?)"\)(?=[^{]*}})',
     r"=\(t '([\s\S]*?)'\)(?=[^{]*}})",