In Pastel/index.less:

Starting from Atom v1.13.0, the contents of atom-text-editor elements are no longer encapsulated within a shadow DOM boundary. This means you should stop using :host and ::shadow pseudo-selectors, and prepend all your syntax selectors with syntax--. To prevent breakage with existing style sheets, Atom will automatically upgrade the following selectors:

• atom-text-editor, :host => atom-text-editor,atom-text-editor

• atom-text-editor .invisible-character, :host .invisible-character, atom-text-editor .indent-guide, :host .indent-guide => atom-text-editor .invisible-character,atom-text-editor .invisible-character, atom-text-editor .indent-guide,atom-text-editor .indent-guide

• atom-text-editor .gutter, :host .gutter => atom-text-editor .gutter,atom-text-editor .gutter

• atom-text-editor .is-focused .cursor, :host .is-focused .cursor => atom-text-editor .is-focused .cursor,atom-text-editor .is-focused .cursor

• atom-text-editor .selection .region, :host .selection .region => atom-text-editor .selection .region,atom-text-editor .selection .region

• atom-text-editor .line-number.cursor-line, :host .line-number.cursor-line, atom-text-editor .atom-text-editor.is-focused .line.cursor-line, :host .atom-text-editor.is-focused .line.cursor-line => atom-text-editor .line-number.cursor-line,atom-text-editor .line-number.cursor-line, atom-text-editor .atom-text-editor.is-focused .line.cursor-line,atom-text-editor .atom-text-editor.is-focused .line.cursor-line

• atom-text-editor .bracket-matcher .region, :host .bracket-matcher .region => atom-text-editor .bracket-matcher .region,atom-text-editor .bracket-matcher .region

• atom-text-editor .comment, :host .comment => atom-text-editor .syntax--comment,atom-text-editor .syntax--comment

• atom-text-editor .invalid.deprecated, :host .invalid.deprecated => atom-text-editor .syntax--invalid.syntax--deprecated,atom-text-editor .syntax--invalid.syntax--deprecated

• atom-text-editor .string, :host .string => atom-text-editor .syntax--string,atom-text-editor .syntax--string

• atom-text-editor .string .constant.character.escape, :host .string .constant.character.escape => atom-text-editor .syntax--string .syntax--constant.syntax--character.syntax--escape,atom-text-editor .syntax--string .syntax--constant.syntax--character.syntax--escape

• atom-text-editor .string.regexp, :host .string.regexp => atom-text-editor .syntax--string.syntax--regexp,atom-text-editor .syntax--string.syntax--regexp

• atom-text-editor .string.regexp .source.ruby.embedded, :host .string.regexp .source.ruby.embedded, atom-text-editor .string.regexp .string.regexp.arbitrary-repitition, :host .string.regexp .string.regexp.arbitrary-repitition => atom-text-editor .syntax--string.syntax--regexp .syntax--source.syntax--ruby.syntax--embedded,atom-text-editor .syntax--string.syntax--regexp .syntax--source.syntax--ruby.syntax--embedded, atom-text-editor .syntax--string.syntax--regexp .syntax--string.syntax--regexp.syntax--arbitrary-repitition,atom-text-editor .syntax--string.syntax--regexp .syntax--string.syntax--regexp.syntax--arbitrary-repitition

• atom-text-editor .constant, :host .constant => atom-text-editor .syntax--constant,atom-text-editor .syntax--constant

• atom-text-editor .variable, :host .variable, atom-text-editor .variable.parameter, :host .variable.parameter, atom-text-editor .variable.other, :host .variable.other => atom-text-editor .syntax--variable,atom-text-editor .syntax--variable, atom-text-editor .syntax--variable.syntax--parameter,atom-text-editor .syntax--variable.syntax--parameter, atom-text-editor .syntax--variable.syntax--other,atom-text-editor .syntax--variable.syntax--other

• atom-text-editor .entity, :host .entity => atom-text-editor .syntax--entity,atom-text-editor .syntax--entity

• atom-text-editor .entity.other.inherited-class, :host .entity.other.inherited-class => atom-text-editor .syntax--entity.syntax--other.syntax--inherited-class,atom-text-editor .syntax--entity.syntax--other.syntax--inherited-class

• atom-text-editor .storage, :host .storage => atom-text-editor .syntax--storage,atom-text-editor .syntax--storage

• .keyword:not(.keyword.operator), .keyword.operator.logical => .syntax--keyword:not(.keyword.operator), .syntax--keyword.syntax--operator.syntax--logical

• .keyword => .syntax--keyword

• .support.type.exception => .syntax--support.syntax--type.syntax--exception

• .entity.other.attribute-name => .syntax--entity.syntax--other.syntax--attribute-name

• .support.constant => .syntax--support.syntax--constant

• .support.type, .support.class => .syntax--support.syntax--type, .syntax--support.syntax--class

• .support.other.variable => .syntax--support.syntax--other.syntax--variable

• .invalid => .syntax--invalid

• .comment => .syntax--comment

• .meta.function.section => .syntax--meta.syntax--function.syntax--section

• .markup.deleted => .syntax--markup.syntax--deleted

• .markup.inserted => .syntax--markup.syntax--inserted

• .markup.changed => .syntax--markup.syntax--changed

Automatic translation of selectors will be removed in a few release cycles to minimize startup time. Please, make sure to upgrade the above selectors as soon as possible.