Private NuGet repository not accessible from fsx file (XmlException: Data at the root level is invalid)

Description

I've deployed a Nexus repository and put a library in its Nuget repo. Now I'm trying to access this artifact from a fsx script but it is failing whereas I can get the artifact xml with curl.

Repro steps

1. A failing fsx example (my artifacts in Nexus are accessible anonymously, you should be able to access it)

open System

open Fake.IO
#r "paket:
source https://packages.antvoice.com/repository/nuget-group/

nuget AntVoiceBuild 0.11.20210521.3 
//"
#load "./.fake/build.fsx/intellisense.fsx"

open IncrementalBuild

printfn "Hello world"

2. Run the command dotnet fake run test.fsx

Expected behavior

The artifact is downloaded correctly

Actual behavior

Paket is failing with the following error :

There was a problem while setting up the environment:
-> Unable to retrieve package versions for 'AntVoiceBuild'
   -- CLOSED --
      
   -- OPEN ----
      AntVoiceBuild 0.11.20210521.3 (from /work/nodev/.fake/test.fsx/paket.dependencies)
-> One or more errors occurred. (One or more errors occurred. (Could not find versions for package AntVoiceBuild on https://packages.antvoice.com/repository/nuget-group. (Source 'https://packages.antvoice.com/repository/nuget-group' yielded no results (Request 'https://packages.antvoice.com/repository/nuget-group/FindPackagesById()?semVerLevel=2.0.0&id='AntVoiceBuild'' finished with error) (Request 'https://packages.antvoice.com/repository/nuget-group/Packages?semVerLevel=2.0.0&$filter=Id eq 'AntVoiceBuild'' finished with error))))
-> One or more errors occurred. (Could not find versions for package AntVoiceBuild on https://packages.antvoice.com/repository/nuget-group. (Source 'https://packages.antvoice.com/repository/nuget-group' yielded no results (Request 'https://packages.antvoice.com/repository/nuget-group/FindPackagesById()?semVerLevel=2.0.0&id='AntVoiceBuild'' finished with error) (Request 'https://packages.antvoice.com/repository/nuget-group/Packages?semVerLevel=2.0.0&$filter=Id eq 'AntVoiceBuild'' finished with error)))
-> Could not find versions for package AntVoiceBuild on https://packages.antvoice.com/repository/nuget-group. (Source 'https://packages.antvoice.com/repository/nuget-group' yielded no results (Request 'https://packages.antvoice.com/repository/nuget-group/FindPackagesById()?semVerLevel=2.0.0&id='AntVoiceBuild'' finished with error) (Request 'https://packages.antvoice.com/repository/nuget-group/Packages?semVerLevel=2.0.0&$filter=Id eq 'AntVoiceBuild'' finished with error))
-> Source 'https://packages.antvoice.com/repository/nuget-group' yielded no results (Request 'https://packages.antvoice.com/repository/nuget-group/FindPackagesById()?semVerLevel=2.0.0&id='AntVoiceBuild'' finished with error) (Request 'https://packages.antvoice.com/repository/nuget-group/Packages?semVerLevel=2.0.0&$filter=Id eq 'AntVoiceBuild'' finished with error)
	-  Request 'https://packages.antvoice.com/repository/nuget-group/FindPackagesById()?semVerLevel=2.0.0&id='AntVoiceBuild'' finished with error
	-> XmlException: Data at the root level is invalid. Line 1, position 1.
	-  Request 'https://packages.antvoice.com/repository/nuget-group/Packages?semVerLevel=2.0.0&$filter=Id eq 'AntVoiceBuild'' finished with error
	-> XmlException: Data at the root level is invalid. Line 1, position 1.

Additional information

If I run the following command I can get what seem to be a correctly formated XML :
curl -iX GET "https://packages.antvoice.com/repository/nuget-group/Packages?semVerLevel=2.0.0&$filter=tolower(Id)%20eq%20'antvoicebuild'"

Remark that I encoded the 2 spaces arround eq because if I don't, Nexus is complaining with

  <p><b>400.</b> <ins>That’s an error.</ins>
  <p>Your client has issued a malformed or illegal request.  <ins>That’s all we know.</ins>

Which could explain why Paket is failing to parse the XML.

When encoding the spaces, it gives :

HTTP/2 200 
date: Fri, 21 May 2021 11:31:45 GMT
server: Nexus/3.29.2-02 (OSS)
x-content-type-options: nosniff
content-security-policy: sandbox allow-forms allow-modals allow-popups allow-presentation allow-scripts allow-top-navigation
x-xss-protection: 1; mode=block
content-type: application/xml
content-length: 3007
via: 1.1 google
alt-svc: clear

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<feed xml:base="https://packages.antvoice.com/repository/nuget-group/" xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns="http://www.w3.org/2005/Atom">
  <title type="text">Packages</title>
  <id>https://packages.antvoice.com/repository/nuget-group/Packages</id>
  <updated>2021-05-21T11:31:45.960Z</updated>
  <link rel="self" title="Packages" href="Packages"/>
  <m:count>0</m:count>
  <entry>
    <id>https://packages.antvoice.com/repository/nuget-group/Packages(Id='AntVoiceBuild',Version='0.11.20210521.3')</id>
    <title type="text">AntVoiceBuild</title>
    <summary type="text">Package Description</summary>
    <updated>2021-05-21T11:12:25.510Z</updated>
    <author>
      <name>AntVoiceBuild</name>
    </author>
    <link rel="edit-media" title="V2FeedPackage" href="Packages(Id='AntVoiceBuild',Version='0.11.20210521.3')/$value" />
    <link rel="edit" title="V2FeedPackage" href="Packages(Id='AntVoiceBuild',Version='0.11.20210521.3')" />
    <category term="NuGetGallery.V2FeedPackage" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" />
    <content type="application/zip" src="https://packages.antvoice.com/repository/nuget-group/AntVoiceBuild/0.11.20210521.3" />
    <m:properties>
      <d:Version>0.11.20210521.3</d:Version>
      <d:Copyright m:null="true"></d:Copyright>
      <d:Created m:type="Edm.DateTime">2021-05-21T11:12:25.515Z</d:Created>
      <d:Dependencies>FSharp.Core:4.3.4:netstandard20|FSharp.Data:3.0.1:netstandard20|Google.Cloud.Storage.V1:2.3.0:netstandard20</d:Dependencies>
      <d:Description>Package Description</d:Description>
      <d:DownloadCount m:type="Edm.Int32">0</d:DownloadCount>
      <d:GalleryDetailsUrl m:null="true"></d:GalleryDetailsUrl>
      <d:IconUrl m:null="true"></d:IconUrl>
      <d:IsLatestVersion m:type="Edm.Boolean">true</d:IsLatestVersion>
      <d:IsAbsoluteLatestVersion m:type="Edm.Boolean">true</d:IsAbsoluteLatestVersion>
      <d:IsPrerelease m:type="Edm.Boolean">false</d:IsPrerelease>
      <d:Published m:type="Edm.DateTime">2021-05-21T11:12:25.515Z</d:Published>
      <d:Language m:null="true"></d:Language>
      <d:LicenseUrl m:null="true"></d:LicenseUrl>
      <d:PackageHash>e242MOXKjUKWmsS9/m4v4YYIapuAs+Rlk6uhdX0S/tcb4fu7eXURDFhR3jDy3eEn9Ti8M3+kOz7bRVTeDOexqw==</d:PackageHash>
      <d:PackageHashAlgorithm>SHA512</d:PackageHashAlgorithm>
      <d:PackageSize m:type="Edm.Int64">43931</d:PackageSize>
      <d:ProjectUrl m:null="true"></d:ProjectUrl>
      <d:ReportAbuseUrl m:null="true"></d:ReportAbuseUrl>
      <d:ReleaseNotes m:null="true"></d:ReleaseNotes>
      <d:RequireLicenseAcceptance m:type="Edm.Boolean">false</d:RequireLicenseAcceptance>
      <d:Tags m:null="true"></d:Tags>
      <d:Title>AntVoiceBuild</d:Title>
      <d:VersionDownloadCount m:type="Edm.Int32">0</d:VersionDownloadCount>
    </m:properties>
  </entry>
</feed>

Start with the failing fsx example and run dotnet fake run test.fsx against the Nexus NuGet source. Inspect how Paket constructs requests to FindPackagesById() and Packages?semVerLevel=2.0.0, comparing them with the working curl request. Done means the package version is discovered and downloaded without the XmlException.