Loading fixtures in the browser broken since v21.3.1

[achingbrain]

Tests that previously passed now fail with

ipfs-http-client: HeadlessChrome 80.0.3987 (Linux 0.0.0) ERROR
ipfs-http-client:   Uncaught Error: Could not get the Fixture: test/fixtures/test-folder/pp.txt
ipfs-http-client:   at /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/fixtures.browser.js:27:1 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:183:5
ipfs-http-client:   
ipfs-http-client:   Error: Could not get the Fixture: test/fixtures/test-folder/pp.txt
ipfs-http-client:       at syncXhr (/home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/fixtures.browser.js:27:1 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:183:11)
ipfs-http-client:       at loadFixtures (/home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/fixtures.browser.js:5:1 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:161:10)
ipfs-http-client:       at Object.../interface-ipfs-core/src/utils/index.js (/home/travis/build/ipfs/js-ipfs/packages/interface-ipfs-core/src/utils/index.js:9:1 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:125728:17)
ipfs-http-client:       at __webpack_require__ (/home/travis/build/ipfs/js-ipfs/packages/ipfs-http-client/webpack/bootstrap:19:1 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:21:30)
ipfs-http-client:       at Object.<anonymous> (/home/travis/build/ipfs/js-ipfs/packages/interface-ipfs-core/src/add.js:6:5 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:114213:5)
ipfs-http-client:       at Object.../interface-ipfs-core/src/add.js (/home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:114730:30)
ipfs-http-client:       at __webpack_require__ (/home/travis/build/ipfs/js-ipfs/packages/ipfs-http-client/webpack/bootstrap:19:1 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:21:30)
ipfs-http-client:       at Object.../interface-ipfs-core/src/index.js (/home/travis/build/ipfs/js-ipfs/packages/interface-ipfs-core/src/index.js:8:8 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:120289:8)
ipfs-http-client:       at __webpack_require__ (/home/travis/build/ipfs/js-ipfs/packages/ipfs-http-client/webpack/bootstrap:19:1 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:21:30)
ipfs-http-client:       at Object.<anonymous> (/home/travis/build/ipfs/js-ipfs/packages/ipfs-http-client/test/interface.spec.js:4:15 <- /home/travis/build/ipfs/js-ipfs/node_modules/aegir/src/config/karma-entry.js:133422:15)

Temporary workaround is to pin aegir to 21.3.0