Checkstyle: CheckstyleException: Unable to find but file exists

My Checkstyle configuration cannot seem to find my suppressions.xml, but it does exist and the filepath it is using works. Both my checkstyle.xml and suppressions.xml are in config/checkstyle. My checkstyle.xml has this:

<module name="SuppressionFilter">
    <property name="file" value="${config_loc}\suppressions.xml"/>
    <property name="optional" value="false"/>
</module>

When I run gradlew check --stacktrace, the stack trace shows this:

Caused by: com.puppycrawl.tools.checkstyle.api.CheckstyleException: Unable to find: C:\Users\ntroncoso\Online Drive\projects\test-project\test-project-sdk\config\checkstyle\suppressions.xml
        at com.puppycrawl.tools.checkstyle.filters.SuppressionsLoader.getSuppressionLoader(SuppressionsLoader.java:287)
        at com.puppycrawl.tools.checkstyle.filters.SuppressionsLoader.loadSuppressions(SuppressionsLoader.java:238)
        at com.puppycrawl.tools.checkstyle.filters.SuppressionsLoader.loadSuppressions(SuppressionsLoader.java:224)
        at com.puppycrawl.tools.checkstyle.filters.SuppressionFilter.finishLocalSetup(SuppressionFilter.java:269)
        at com.puppycrawl.tools.checkstyle.api.AutomaticBean.configure(AutomaticBean.java:197)
        at com.puppycrawl.tools.checkstyle.Checker.setupChild(Checker.java:477)
        ... 206 more
Caused by: java.io.FileNotFoundException: http://www.puppycrawl.com/dtds/configuration_1_3.dtd
        at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:647)
        at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startEntity(XMLEntityManager.java:1304)
        at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startDTDEntity(XMLEntityManager.java:1270)
        at com.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.setInputSource(XMLDTDScannerImpl.java:264)
        at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.dispatch(XMLDocumentScannerImpl.java:1161)
        at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.next(XMLDocumentScannerImpl.java:1045)
        at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:959)
        at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602)
        at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505)
        at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:842)
        at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:771)
        at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
        at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
        at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643)
        at com.puppycrawl.tools.checkstyle.XmlLoader.parseInputSource(XmlLoader.java:86)
        at com.puppycrawl.tools.checkstyle.filters.SuppressionsLoader.getSuppressionLoader(SuppressionsLoader.java:283)

As I mentioned, I can copy and paste that file path into file explorer and it'll open. I tried just hardcoding the full path as well, but I get the same error. The only thing I can think of is the \ntroncoso part. Some systems will treat that as a new line in the path. But typically, the error would also print the new line, so I don't feel like that's the issue.

> FileNotFoundException: http://www.puppycrawl.com/dtds/configuration_1_3.dtd

This is your true error. The DTD of your suppression file is wrong. First, you are using a configuration DTD for a suppression file. Second, puppycrawl domain is outdated and has since moved to checkstyle.org .

The DTD should be changed to https://checkstyle.org/dtds/suppressions_1_2.dtd which is the latest DTD for the latest version of Checkstyle at this time.

Please see https://github.com/checkstyle/checkstyle/blob/master/config/suppressions.xml for an example of a proper suppression file.