--extra-css not working

I have added a path to my extra.css:

"--extra-css=os.path.join(Xslt.xslt_dir, self.uid, 'extra.css')",

When I paste this css into the GUI the css has the intendent effect, but when adding it in the command line it has no effect.

I get some error indications in the Python log file:

[28.8044s] Conversion options changed from defaults:

[28.8044s] docx_page_margin_bottom: 42.0

[28.8044s] language: u' (nb) '

[28.8044s] toc_threshold: 0

[28.8044s] font_size_mapping: u'13,13,13,13,13,13,13,13'

[28.8044s] base_font_size: 13

[28.8044s] docx_page_margin_top: 42.0

[28.8044s] extra_css: u"os.path.join(Xslt.xslt_dir, self.uid, 'extra.css')"

[28.8044s] docx_page_margin_right: 56.0

[28.8044s] docx_page_size: u'a4'

[28.8044s] docx_page_margin_left: 70.0

[28.8044s] embed_font_family: u'Verdana'

[28.8044s] no_chapters_in_toc: True

[28.8044s] 1% Konverterer inndata til HTML...

[28.8045s] InputFormatPlugin: HTML Input running

[28.8045s] on /tmp/tmpcguaglp6/EPUB/861011.xhtml

[28.8045s] Building file list...

[28.8045s] Normalizing filename cases

[28.8045s] Rewriting HTML links

[28.8045s] 34% Running transforms on e-book...

[28.8045s] Merging user specified metadata...

[28.8045s] Detecting structure...

[28.8045s] Auto generated TOC with 0 entries.

[28.8045s] Flattening CSS and remapping font sizes...

[28.8045s] Embedding font: Verdana

[28.8045s] Property: Unknown Property name. [1:42: panose-1]

[28.8045s] Property: Unknown Property name. [1:49: panose-1]

[28.8045s] Property: Unknown Property name. [1:47: panose-1]

[28.8045s] Property: Unknown Property name. [1:54: panose-1]

[28.8045s] CSSStyleRule: No start { of style declaration found: u"os.path.join(Xslt.xslt_dir, self.uid, 'extra.css')" [1:51: ]

[28.8045s] Selector: Unexpected CHAR. [1:8: .]

[28.8045s] Unexpected token (FUNCTION, join(, 1, 9)

[28.8045s] Selector: Unexpected IDENT. [1:14: Xslt]

[28.8045s] Selector: Single selector only. [1:27: ,]

[28.8045s] Selector: Single selector only. [1:37: ,]

[28.8045s] Selector: Unexpected STRING. [1:39: 'extra.css']

[28.8045s] Selector: Unexpected CHAR. [1:50: )]

[28.8045s] SelectorList: Invalid Selector: os.path.join(Xslt.xslt_dir, self.uid, 'extra.css')

[28.8045s] CSSStyleRule: No style declaration or "}" found: u"os.path.join(Xslt.xslt_dir, self.uid, 'extra.css')"

[28.8045s] Source base font size is 12.00000pt

[28.8045s] Removing fake margins...

[28.8045s] Cleaning up manifest... :smack: