Textmate's gettext syntax highlighting, with an updated regex which does show blank lines as block red. https://github.com/textmate/gettext.tmbundle/blob/master/Syntaxes/Gettext.tmLanguage

Gettext.tmLanguage

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>comment</key>
	<string>
TODO:  Command for copy original to untranslated, label as fuzzy, remove fuzzy, next fuzzy etc
Create meta scope for each entry
</string>
	<key>fileTypes</key>
	<array>
		<string>po</string>
		<string>potx</string>
	</array>
	<key>keyEquivalent</key>
	<string>^~G</string>
	<key>name</key>
	<string>Gettext</string>
	<key>patterns</key>
	<array>
		<dict>
			<key>begin</key>
			<string>msgid\s+""</string>
			<key>end</key>
			<string>^$</string>
			<key>name</key>
			<string>entity.name.section.header.po</string>
		</dict>
		<dict>
			<key>captures</key>
			<dict>
				<key>1</key>
				<dict>
					<key>name</key>
					<string>constant.character.double-quote.po</string>
				</dict>
				<key>2</key>
				<dict>
					<key>name</key>
					<string>string.quoted.double.po</string>
				</dict>
				<key>3</key>
				<dict>
					<key>name</key>
					<string>constant.character.double-quote.po</string>
				</dict>
			</dict>
			<key>match</key>
			<string>^msgid(?:_plural)?\s+(")(.*)(")\s*$</string>
			<key>name</key>
			<string>keyword.control.msgid.po</string>
		</dict>
		<dict>
			<key>captures</key>
			<dict>
				<key>1</key>
				<dict>
					<key>name</key>
					<string>constant.character.double-quote.po</string>
				</dict>
				<key>2</key>
				<dict>
					<key>name</key>
					<string>string.quoted.double.po</string>
				</dict>
				<key>3</key>
				<dict>
					<key>name</key>
					<string>constant.character.double-quote.po</string>
				</dict>
			</dict>
			<key>match</key>
			<string>^msgstr(?:\[\d?\])?\s+(")(.*)(")\s*$</string>
			<key>name</key>
			<string>keyword.control.msgstr.po</string>
		</dict>
		<dict>
			<key>captures</key>
			<dict>
				<key>1</key>
				<dict>
					<key>name</key>
					<string>constant.character.double-quote.po</string>
				</dict>
				<key>2</key>
				<dict>
					<key>name</key>
					<string>string.quoted.double.po</string>
				</dict>
				<key>3</key>
				<dict>
					<key>name</key>
					<string>constant.character.double-quote.po</string>
				</dict>
			</dict>
			<key>match</key>
			<string>^msgctxt(?:\[\d?\])?\s+(")(.*)(")\s*$</string>
			<key>name</key>
			<string>keyword.control.msgctxt.po</string>
		</dict>
		<dict>
			<key>captures</key>
			<dict>
				<key>1</key>
				<dict>
					<key>name</key>
					<string>constant.character.double-quote.po</string>
				</dict>
				<key>2</key>
				<dict>
					<key>name</key>
					<string>string.quoted.double.po</string>
				</dict>
				<key>3</key>
				<dict>
					<key>name</key>
					<string>constant.character.double-quote.po</string>
				</dict>
			</dict>
			<key>match</key>
			<string>^(")(.+)(")\s*$</string>
			<key>name</key>
			<string>string.quoted.double.po</string>
		</dict>
		<dict>
			<key>match</key>
			<string>^#\s+(.*)\s*$</string>
			<key>name</key>
			<string>comment.line.number-sign.po</string>
		</dict>
		<dict>
			<key>captures</key>
			<dict>
				<key>1</key>
				<dict>
					<key>name</key>
					<string>keyword.other.flag.po</string>
				</dict>
			</dict>
			<key>match</key>
			<string>^#,\s+((?:(?:fuzzy)|(?:no-)?(?:c|objc|sh|lisp|elisp|librep|scheme|smalltalk|java|csharp|awk|object-pascal|ycp|tcl|perl|perl-brace|php|gcc-internal|qt|boost)-format)(?:,\s*(?:(?:fuzzy)|(?:no-)?(?:c|objc|sh|lisp|elisp|librep|scheme|smalltalk|java|csharp|awk|object-pascal|ycp|tcl|perl|perl-brace|php|gcc-internal|qt|boost)-format))*)\s*$</string>
			<key>name</key>
			<string>comment.line.number-sign.flag.po</string>
		</dict>
		<dict>
			<key>match</key>
			<string>^#\.\s+(.*)\s*$</string>
			<key>name</key>
			<string>comment.line.number-sign.extracted.po</string>
		</dict>
		<dict>
			<key>captures</key>
			<dict>
				<key>1</key>
				<dict>
					<key>name</key>
					<string>constant.character.sourceref.po</string>
				</dict>
				<key>3</key>
				<dict>
					<key>name</key>
					<string>constant.numeric.linenumber.po</string>
				</dict>
			</dict>
			<key>match</key>
			<string>^#:\s+((.*))(:([\d;]*))\s*$</string>
			<key>name</key>
			<string>comment.line.number-sign.reference.po</string>
		</dict>
		<dict>
			<key>match</key>
			<string>^#|\s+(msgid|msgctxt)\s+(".*")\s*$</string>
			<key>name</key>
			<string>comment.line.number-sign.previous.po</string>
		</dict>
		<dict>
			<key>comment</key>
			<string>a line that does not begin with # or ". Could improve this regexp</string>
			<key>match</key>
			<string>^[^#"].+$</string>
			<key>name</key>
			<string>invalid.illegal.po</string>
		</dict>
	</array>
	<key>scopeName</key>
	<string>source.po</string>
	<key>uuid</key>
	<string>F07730BD-59BC-41D0-AC3F-4AB2DCB6C54A</string>
</dict>
</plist>