Should I be able to import a gzipped BED file from a URL? I'm unsure if this is user error or a bug in rtracklayer::import(). Any advice is appreciated:

> suppressPackageStartupMessages(library(rtracklayer))
# Directly import()-ing fails
> import(BEDFile("http://hgdownload.cse.ucsc.edu/goldenPath/hg19/encodeDCC/wgEncodeMapability/wgEncodeDacMapabilityConsensusExcludable.bed.gz"))
Error in pushBack(line, con) :
  can only push back on text-mode connections

# Downloading and then importing works
> a <- tempdir()
> download.file("http://hgdownload.cse.ucsc.edu/goldenPath/hg19/encodeDCC/wgEncodeMapability/wgEncodeDacMapabilityConsensusExcludable.bed.gz", destfile = file.path(a, "wgEncodeDacMapabilityConsensusExcludable.bed.gz"))
trying URL 'http://hgdownload.cse.ucsc.edu/goldenPath/hg19/encodeDCC/wgEncodeMapability/wgEncodeDacMapabilityConsensusExcludable.bed.gz'
Content type 'application/x-gzip' length 4731 bytes
==================================================
downloaded 4731 bytes

> import(file.path(a, "wgEncodeDacMapabilityConsensusExcludable.bed.gz"))
GRanges object with 411 ranges and 2 metadata columns:
        seqnames               ranges strand |                    name
           <Rle>            <IRanges>  <Rle> |             <character>
    [1]     chr1   [ 564450,  570371]      * | High_Mappability_island
    [2]     chr1   [ 724137,  727043]      * |        Satellite_repeat
    [3]     chr1   [ 825007,  825115]      * |                BSR/Beta
    [4]     chr1   [2583335, 2634374]      * |  Low_mappability_island
    [5]     chr1   [4363065, 4363242]      * |                (CATTC)n
    ...      ...                  ...    ... .                     ...
  [407]     chrY [28555027, 28555353]      * |                    TAR1
  [408]     chrY [28784130, 28819695]      * |        Satellite_repeat
  [409]     chrY [58819368, 58917648]      * |                (CATTC)n
  [410]     chrY [58971914, 58997782]      * |                (CATTC)n
  [411]     chrY [59361268, 59362785]      * |                    TAR1
            score
        <numeric>
    [1]      1000
    [2]      1000
    [3]      1000
    [4]      1000
    [5]      1000
    ...       ...
  [407]      1000
  [408]      1000
  [409]      1000
  [410]      1000
  [411]      1000
  -------
  seqinfo: 25 sequences from an unspecified genome; no seqlengths

> sessionInfo()
R Under development (unstable) (2016-03-11 r70310)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.11.3 (El Capitan)

locale:
[1] en_AU.UTF-8/en_AU.UTF-8/en_AU.UTF-8/C/en_AU.UTF-8/en_AU.UTF-8

attached base packages:
[1] stats4    parallel  stats     graphics  grDevices utils     datasets
[8] methods   base

other attached packages:
[1] rtracklayer_1.31.7    GenomicRanges_1.23.24 GenomeInfoDb_1.7.6
[4] IRanges_2.5.40        S4Vectors_0.9.43      BiocGenerics_0.17.3
[7] repete_0.0.0.9002     devtools_1.10.0

loaded via a namespace (and not attached):
 [1] Rcpp_0.12.3                 XVector_0.11.7
 [3] magrittr_1.5                zlibbioc_1.17.1
 [5] GenomicAlignments_1.7.20    BiocParallel_1.5.20
 [7] stringr_1.0.0               tools_3.3.0
 [9] SummarizedExperiment_1.1.22 Biobase_2.31.3
[11] digest_0.6.9                pryr_0.1.2
[13] bitops_1.0-6                codetools_0.2-14
[15] RCurl_1.95-4.8              memoise_1.0.0
[17] stringi_1.0-1               Biostrings_2.39.12
[19] Rsamtools_1.23.5            XML_3.98-1.4

It's true that pushBack() will not work with gzcon(). That's because it's always binary. I'm not sure why it does not have the option for text mode. Will raise this issue with R core.